Strange. Is this happening only in one particular world, or everywhere?

might be a false alarm. It sometimes crashes unexpectedly even while carrying vanilla mobs, so I stopped using it too much.
from what I see it locks opening inventory and scrolling, carrying a mob turns it into an item.
When you die while carrying it and keepInventory=true then scrolling/opening inventory crashes.

When you die while carrying it and keepInventory=true then scrolling/opening inventory crashes.

Interesting, I've not thought about keepInventory. I'm gonna take a look at that
Edit: It doesn't crash me though. It also doesn't lock the slot, so you're able to move the carry-item freely around your inventory.

Ok, this has been resolved with a workaround: When dying with keepInventory, the Block/Entity still gets placed in the world, but at your respawn location instead of your death location

the log is too large to send the whole thing
https://paste.ubuntu.com/25830090/