This issue has been raised here before. We have played quite a few maps where the red chain appears and I cannot see my friend when I host en sometimes he cannot see me. This is not a connectivtity issue. Our pings are below 30.
This might also cause the incorrect marking of all objectives to failed/completed when starting a new game or loading and savegame. Logged in 0017305.

I see lots of actions logged to fix cosmetic things when basic features in the game like loading/saving and coop is broken. Rather fix these important issues first. This is extremely frustrating. The game is long out of Aplha and Beta and we are still sitting with these type of fundemental issues. This could still be tolerated in Aplha and Beta but now that the commercial release is out these things should not happen and be resolved ASAP.