Haven't seen any other posts regarding hand bug occurring however this has been happening consistently over the past few weeks.

Hand Bug: Bugged hand slot where the player is unable to remove item in hand or swap it with another.

It's simple to replicate:
Simply swapping between items too fast will result in the hand bug
I've tried this across many different servers. Vanilla / Lightly Modded / Modded
and without failure it is plaguing my game.

Relogging is the only fix as far as I know.