Today on multiplayer:
Cruising around 52000 feet, at about M1.1-1.2, with both a centerline fuel tank and wing tanks. Aircraft started to shake a bit, then went into an aggressive, unrecoverable roll. I hit the emergency jettison switch to drop my tanks, plane kept rolling. Turned off the FBW gain switch, still nothing. Full left stick did nothing to stop the roll, either.
I'm guessing it had something to do with transonic/supersonic flight with wing tanks. The aircraft maintained approximately M1 all the way to the ground with speed brakes out.