When you try to pick up an entity (villager, zombie, etc) using carry on mod, Inventory profiles tries to put this on the hot bar, causing this entity to disapear and keeping slowness effect.

It is also informed on Carry On github.
Tschipp/CarryOn#409

Possible solution: Verify if carry on is installed. If it is, deactivate "Pick items directly into the inventory" on Locked Slots options by default.

Yeah same problem also exists if the hot bar slots are locked.

and only in multiplayer games.

I'll probably add filter for carryon: items