Hello there,
we play MP in a group of 4, regardless of who is hosting we have the same problem.
When playing "on foot" everything is fine, but as soon as one of us just gets in the car and drives, glitching occurs - we can't see the car move, if 2 people are sitting in the car, for the passenger the car doesn't move, and when they get out the car is still in the same position. This leads to another problem with teleporting zombies etc. etc.
Also, we suddenly have invisible walls (darker areas on the map, like a cloud shadow).
Do you have any suggestions? What could be wrong?