Hello, a few days ago I encountered this bug. With PvP off, a friend and I were bridging across the End, I was crouching with a shield in my offhand and placing blocks in front of me with my back to the other player, they shot me with a Punch II bow and the effect was applied to me although PvP was not enabled. I fell into the void and my items were lost.

Steps to reproduce:

1. Equip shield and crouch
2. Face opposite of another player
3. Have the other player shoot you with a Punch II bow

You should have the Punch effect applied to you.