I found shulker which has a lot of shulker bombs stuck in it. It was shooting normaly, however dealing a lot of damage(half of my hp and I was full netherite). The shulker was behaving abnormaly as it was opening and closing frequently. I found this shulker in glitched endcity that was already reported. This bug happened on my spigot 1.16.5 server and I use Java version 8 update 281.