i was playing minecraft in creative on my realm and i was building in the end, i  was done with my build and i left my realm and when i came back to it everything looked okay, until i went over to the ender dragon and i saw the boss bar, the ender crystals, and then i heard the ender dragon noise and then it crashed, i didn't see the ender dragon though, it went to the time out screen, but instead it would say either "server closed" "io.netty.channel.AbstractChannel$AnnotatedConnectException:syscall:getsockopt(...) failed: Connection refused:" or it would say something about java, sorry i couldn't recreate the last one, then i tried to get back in but it said the same thing, closing and reopening minecraft seemed to work but then trying to get back in didn't work, i luckily backed it up so i went to my backup but if i went towards the ender dragon it did the same thing, i tried to kill it with commands but it said "no entity was found", i restarted my computer but the same thing happened, i hope that you will be able to fix this.(edit: seems to be a ticking entity, don't know why though)