I had a severe lag spike while playing with friends for a bit. After it stopped, I encountered the following:
1. When enemies were killed their model would stay in the game.
2. All of the new enemies were completely invisible to me.
3. I could take damage but for some reason it wouldn't go below 2%, resulting in a "godmode" (I had some boosters to increase health regen but it's likely something else).
I confirmed I wasn't lagging anymore because everyone else was able to see me getting attacked by like 20 enemies while taking no damage.