Mine went nuts last night on a flight from KATL to KLAX.  Running at 4x speed once I reached cruise at FL380, after a while it went totally out of control - roll, pitch, yaw went completely bonkers, and IAS dropped all the way to zero....no way to recover, all on board perished in the crash.  :'(

Maybe this plane becomes unstable at 4x speed or above?  I had no such problems with the CS 767 from KLAX to KATL the other day, also running at 4x while in cruise.