Pitching down.

[RichFlight22]

Sometimes, especially on a high altitude, when all functions of autopilot (speed, heading) except altitude are on, I can't turn the altitude autopilot on, or the plane will come into an uncontrollable pitch down.

[Gamer1029384756]

Happened to me too. I think it's because the trim gets set to maximum pitch down. Try pressing the 'Delete' button immediately after it happens.

[Gamer1029384756]

Still waiting for a permanent fix.

[ICommandZombI]

Me too but sometimes pitch up and sometimes down