I encountered this problem (and yes, in 2017!), Specifically, under Commando Mastery, I had 196/200 waves for Asari Vanguard. When it reached finally 200 my game would trigger an error at the end of the wave complaining that it lost connection with the server, and kick me out.
Commando Mastery 10/12 (everything good at this point)
- Asari Vanguard waves: 196/200, completed: 0.
I join a game. After four waves, I get a little notification popup that Asari Vanguard waves have been completed, but then get a game error I lost connection with server, and get booted out. My internet connection seems fine, and I can rejoin multiplayer. I join another game. After four waves, I get the same game error that I lost connection with server, and get booted out. I then check my Challenge completion on http://n7hq.masseffect.com and see it is now out of sync (ME3 in-game counter is also out of sync):
Commando Mastery 10/12 (this should be 11/12)
- Asari Vanguard waves: 200/200, completed: 2 (this should be 1, not 2).
Origin application also would complain ME3 was now out of sync with the Cloud. Eventually after checking and unchecking sync with Cloud, I get ME3 to startup, but it looks like Commando Mastery counter is now out of sync as it did not increment itself by one for the two hundred Asari Vanguard wave completion.
