we'Re not sure, if these effect are conneted, but they appear simultaneous like 80% of the time.

1. Lately when I play with friends every now and then enemies are not taking any damage, even on lower difficulties. Usually we retreat from the fight for a couple seconds until damage works again, but often enough we're taking damage from invisible sources, sometimes dying in the process without ever knowing why. AFTER that happens, we usually discover the second issue.
2. After this happens the characters are positioned differently on everyone's map. E.G. we shared screens over Discord and my character stands 1-2m off to the left on his map compared to mine. My friend fired a couple round from his bolter and in my game the shots originated from a couple meters to the right instead of the barrel of his bolter. Sometimes we manage to finish the map anyway, but the issues never really disappear making these maps a nightmare to complete.