Totally Invisible soldiers and hostiles after new DLC installed

Something similar happened to me and my friends except in one game we couldn't see the enemies except for Geth Pyros and Bombers, in another game we got stuck playing against Cerberus because a Nemisis was the last enemy but the game wouldn't register that it was there nor could we kill it. We eventually started shooting at the rafters it had fallen from and it took damage and died. Please fix these bugs asap these were the worst instances but they still occured fairly regularly.