Was playing some multiplayer on the NA seasonal servers with a couple of friends this evening working to get one of them caught up in the campaign and we started experiencing issues similar to last week when the servers were taking a poop. We hung at mission exit and returned to the ship with no loot or experience gained 2 missions in a row. The campaign progress was still advancing for the player we were helping, and when we all broke off to try playing singleplayer everything seems to be working fine.

Edit:
I've started treating this as a log of all the instances my cabal encounters with multiplayer and losing XP/loot on a mission.