Illagers spawning in daytime and invisible, causing items to turn invisible

Put the summary of the bug you're having here

What I expected to happen was...:
Minecraft ran normally, area was lit up with torches and during day cycle

What actually happened was...:
Illagers spawned in when they were not meant to be able to, began to turn invisible during combat and would cause dropped items to become invisible and scatter more than the usual area amount.

Steps to Reproduce:
1. have illagers spawn in survival
2. fight them
3.