That's exactly where shit gets really complicated ^^
1) The software couldn't be relicensed in the first place because there are parts for which they don't own the copyright. Can't relicense something you don't worn. The attempt to change the license of the software is void at best.
2) The AGPL is contagious, forcing all future contributions to be AGPL as well. Their claim that contributions started being under another license at some point is void, because these contributions were necessarily under AGPL.
Notice there's an interesting conundrum in how the two elements interact and create a deadlock. It's on purpose, the GPL/AGPL is meant to prevent relicensing.
It's copyright violations all over the place. There's gotta be a thousand and one ways to make them accountable. You could personally start redistributing/reselling the software assuming it's AGPL so you get some grounds and go after them for saying it's not.