On Nov. 24th my server started crashing randomly and I couldn't understand why. But after several days of investigating I found the cause. I created a guardian farm that can either kill guardians with fall damage in the overworld or send them into the nether via portal to farm for experience due the infinite mob cap. The instant even one guardian goes through a nether portal, my server closes. I press a button and the farm kills the guardian from fall damage and none go through the portal, the server stops crashing. I've tested this several times and guardians entering the nether portal is the root of my issue. Very disappointed because I spent over a month building this farm and it was working perfectly without error for all of the weeks leading up to the release of 1.8.1.

I just did a test and apparently there is a bug with this specific nether portal. When I throw and item through the nether portal and then I jump into the nether portal, I get sent to a completely unconnected nether portal. However, if I just walk through the portal and do not throw an item or mob through the portal it sends me to the correct connected portal. I think this is why when the mob go through the portal, it kicks everyone from the server. I've copied the most recent log of what happened after I threw an item through the nether portal in question and walked through it causing me to get kicked from the server.

[18:39:59] [Client thread/INFO]: Setting user: Zaraxas
[18:39:59] [Client thread/INFO]: (Session ID is token:7b3beff99fc742adb5a247bd42492d92:23085e77411341188315390c9a62f644)
[18:40:01] [Client thread/INFO]: LWJGL Version: 2.9.1
[18:40:01] [Client thread/INFO]: Reloading ResourceManager: Default, Equanimity.zip
[18:40:03] [Sound Library Loader/INFO]: Starting up SoundSystem...
[18:40:03] [Thread-6/INFO]: Initializing LWJGL OpenAL
[18:40:03] [Thread-6/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[18:40:03] [Thread-6/INFO]: OpenAL initialized.
[18:40:04] [Sound Library Loader/INFO]: Sound engine started
[18:40:06] [Client thread/INFO]: Created: 1024x1024 textures-atlas
[18:40:08] [Client thread/INFO]: Realms library version == 1.7.4
[18:40:09] MCO Availability Checker #1/INFO: Realms is available for this user
[19:07:11] [Client thread/INFO]: [CHAT] jgray46 left the game
[19:16:45] [Client thread/ERROR]: Item entity 244757 has no item?!
[19:17:10] [Client thread/ERROR]: Item entity 245003 has no item?!
[19:17:15] [Client thread/ERROR]: Item entity 245048 has no item?!
[19:17:34] [Client thread/ERROR]: Item entity 245266 has no item?!
[19:17:43] [Client thread/ERROR]: Item entity 245386 has no item?!
[19:17:43] [Client thread/ERROR]: Item entity 245386 has no item?!
[19:19:11] [Client thread/ERROR]: Item entity 246671 has no item?!
[19:19:11] [Client thread/ERROR]: Item entity 246671 has no item?!
[19:19:21] [Client thread/ERROR]: Item entity 246782 has no item?!
[19:19:21] [Client thread/ERROR]: Item entity 246782 has no item?!
[19:19:21] [Client thread/ERROR]: Item entity 246782 has no item?!
[19:19:21] [Client thread/ERROR]: Item entity 246782 has no item?!
[19:19:21] [Client thread/ERROR]: Item entity 246782 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:47] [Client thread/ERROR]: Item entity 247257 has no item?!
[19:19:49] [Client thread/ERROR]: Item entity 247314 has no item?!
[19:19:49] [Client thread/ERROR]: Item entity 247314 has no item?!
[19:19:49] [Client thread/ERROR]: Item entity 247314 has no item?!
[19:19:49] [Client thread/ERROR]: Item entity 247314 has no item?!
[19:19:49] [Client thread/ERROR]: Item entity 247314 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:51] [Client thread/ERROR]: Item entity 247343 has no item?!
[19:19:52] [Client thread/ERROR]: Item entity 247345 has no item?!
[19:19:52] [Client thread/ERROR]: Item entity 247345 has no item?!
[19:19:52] [Client thread/ERROR]: Item entity 247345 has no item?!
[19:19:52] [Client thread/ERROR]: Item entity 247345 has no item?!
[19:19:52] [Client thread/ERROR]: Item entity 247345 has no item?!
[19:20:05] [Client thread/ERROR]: Item entity 247477 has no item?!
[19:20:05] [Client thread/ERROR]: Item entity 247477 has no item?!
[19:20:05] [Client thread/ERROR]: Item entity 247477 has no item?!
[19:20:05] [Client thread/ERROR]: Item entity 247477 has no item?!
[19:20:05] [Client thread/ERROR]: Item entity 247477 has no item?!
[19:20:29] [Client thread/ERROR]: Item entity 247896 has no item?!
[19:20:29] [Client thread/ERROR]: Item entity 247896 has no item?!
[19:20:29] [Client thread/ERROR]: Item entity 247896 has no item?!
[19:20:29] [Client thread/ERROR]: Item entity 247896 has no item?!
[19:20:29] [Client thread/ERROR]: Item entity 247896 has no item?!
[19:24:27] [Client thread/ERROR]: Item entity 251661 has no item?!
[19:24:27] [Client thread/ERROR]: Item entity 251661 has no item?!
[19:24:27] [Client thread/ERROR]: Item entity 251661 has no item?!
[19:24:27] [Client thread/ERROR]: Item entity 251661 has no item?!
[19:24:27] [Client thread/ERROR]: Item entity 251661 has no item?!
[19:26:16] [Client thread/ERROR]: Item entity 252556 has no item?!
[19:26:16] [Client thread/ERROR]: Item entity 252556 has no item?!
[19:26:16] [Client thread/ERROR]: Item entity 252556 has no item?!
[19:26:16] [Client thread/ERROR]: Item entity 252556 has no item?!
[19:26:16] [Client thread/ERROR]: Item entity 252556 has no item?!
[19:26:17] [Client thread/ERROR]: Item entity 252557 has no item?!
[19:26:17] [Client thread/ERROR]: Item entity 252557 has no item?!
[19:26:17] [Client thread/ERROR]: Item entity 252557 has no item?!
[19:26:17] [Client thread/ERROR]: Item entity 252557 has no item?!
[19:26:17] [Client thread/ERROR]: Item entity 252557 has no item?!
[19:27:12] [Client thread/ERROR]: Item entity 253220 has no item?!
[19:27:12] [Client thread/ERROR]: Item entity 253220 has no item?!
[19:27:12] [Client thread/ERROR]: Item entity 253220 has no item?!
[19:27:12] [Client thread/ERROR]: Item entity 253220 has no item?!
[19:27:12] [Client thread/ERROR]: Item entity 253220 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:27:18] [Client thread/ERROR]: Item entity 253327 has no item?!
[19:28:20] [Client thread/ERROR]: Item entity 254555 has no item?!
[19:28:33] [Client thread/ERROR]: Item entity 254619 has no item?!
[19:28:34] [Client thread/ERROR]: Item entity 254619 has no item?!
[19:28:34] [Client thread/ERROR]: Item entity 254619 has no item?!
[19:29:58] [Client thread/ERROR]: Item entity 256091 has no item?!
[19:32:31] [Client thread/ERROR]: Item entity 258305 has no item?!
[19:32:31] [Client thread/ERROR]: Item entity 258305 has no item?!
[19:32:31] [Client thread/ERROR]: Item entity 258305 has no item?!
[19:32:31] [Client thread/ERROR]: Item entity 258305 has no item?!
[19:32:31] [Client thread/ERROR]: Item entity 258305 has no item?!
[19:34:36] [Client thread/ERROR]: Item entity 259397 has no item?!
[19:34:36] [Client thread/ERROR]: Item entity 259397 has no item?!
[19:34:36] [Client thread/ERROR]: Item entity 259397 has no item?!
[19:34:36] [Client thread/ERROR]: Item entity 259397 has no item?!
[19:34:36] [Client thread/ERROR]: Item entity 259397 has no item?!
[19:40:15] [Client thread/ERROR]: Item entity 261998 has no item?!
[19:40:15] [Client thread/ERROR]: Item entity 261998 has no item?!
[19:40:15] [Client thread/ERROR]: Item entity 261998 has no item?!
[19:40:15] [Client thread/ERROR]: Item entity 261998 has no item?!
[19:40:15] [Client thread/ERROR]: Item entity 261998 has no item?!
[19:40:20] [Client thread/ERROR]: Item entity 262069 has no item?!
[19:40:20] [Client thread/ERROR]: Item entity 262069 has no item?!
[19:40:20] [Client thread/ERROR]: Item entity 262069 has no item?!
[19:40:20] [Client thread/ERROR]: Item entity 262069 has no item?!
[19:40:20] [Client thread/ERROR]: Item entity 262069 has no item?!
[19:40:39] [Client thread/ERROR]: Item entity 262270 has no item?!
[19:40:39] [Client thread/ERROR]: Item entity 262270 has no item?!
[19:40:39] [Client thread/ERROR]: Item entity 262270 has no item?!
[19:40:39] [Client thread/ERROR]: Item entity 262270 has no item?!
[19:40:39] [Client thread/ERROR]: Item entity 262270 has no item?!
[19:41:27] [Realms-connect-task/ERROR]: Couldn't connect to world
java.net.ConnectException: Connection refused: no further information: ec2-54-145-248-14.compute-1.amazonaws.com/54.145.248.14:27087
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[?:1.7.0_45]
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source) ~[?:1.7.0_45]
at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:208) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:287) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:528) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at java.lang.Thread.run(Unknown Source) ~[?:1.7.0_45]
[19:41:31] [Realms-connect-task/ERROR]: Couldn't connect to world
java.net.ConnectException: Connection refused: no further information: ec2-54-145-248-14.compute-1.amazonaws.com/54.145.248.14:27087
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[?:1.7.0_45]
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source) ~[?:1.7.0_45]
at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:208) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:287) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:528) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at java.lang.Thread.run(Unknown Source) ~[?:1.7.0_45]
[19:41:36] [Realms-connect-task/ERROR]: Couldn't connect to world
java.net.ConnectException: Connection refused: no further information: ec2-54-145-248-14.compute-1.amazonaws.com/54.145.248.14:27087
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[?:1.7.0_45]
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source) ~[?:1.7.0_45]
at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:208) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:287) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:528) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at java.lang.Thread.run(Unknown Source) ~[?:1.7.0_45]
[19:41:42] [Client thread/INFO]: Stopping!
[19:41:42] [Client thread/INFO]: SoundSystem shutting down...
[19:41:42] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com