Enviromental Slabfish Duping Items When Picked Up

[axtrough]

Expected Behavior

The items stay in the slabfish's backpack and doesnt drop out

Actual Behavior

The items just gets dropped out and when I place it down again the items are in the backpack too

Steps to Reproduce

Tame a slabfish with tropical fishes then give him a chest, place something in its inventory then pick him up.

Version of Minecraft, Carry On, Forge

1.16.5, 1.16.5-1.15.5.22, 36.2.20

Screenshots encouraged

https://user-images.githubusercontent.com/77877788/154492467-5d5c2352-a577-4cfc-a68f-2d93bd121618.mp4