Most of the entities in my world (such as item frames, zombies, skeletons, etc.) became invisible after I died (in singleplayer) and I could not see or interact with them directly, however, they could still be affected with commands such as /execute and /effect.
Steps to Reproduce:
1. Have several entities in a world (possibly singleplayer only)
2. Die
3. /effect @e 24
Related issues
Comments

Duplicates MC-68403