there's a problem with inventory click event
When taking an item out of someone else's inventory and placing it into yours, the item auto moves to another location

I place item from other person into my inventory here as shown in this

and moves here instantly when placed

Doesn't happen every time but happens about half the time

using paper 1.16.1 b134 with ess v2.18.0 and v2.18.21
Only essentials was installed when testing this

Also does it with these

with both with Optifine 1.16.1 and default vanilla client
There's no error and using default configs

Pretty sure this has been reported before, it's a spigot bug which Essentials cannot fix.

Please use https://dev.bukkit.org/projects/openinv if you need this bug to go away.