I found this bug in multiplayer and tested it on singleplayer.

Seems like the player's head rotates in different direction whereas the mouse cursor was.

This bug seems to both affect both Vanilla and Modded Minecraft.

Steps to Reproduce:
1. Make a tower that is 3 blocks tall
2. Put a block in the 3rd block
3. Look in 3rd person mode
4. Press E
If you're playing on Creative, press on Survival Inventory and the bug happens. If you're playing on Survival, no need.

Crash report added.

If this is a duplicate, I'm sorry but i can't seem to find the bug in search results.