Falling with AP+

maybe someone can help me out…

AP+ just screwed me over. I left the flight at M 0.84 (A339). I come back and im falling to the ground… instantly. No time to even settle in comfortably.

Why is this?

What was your weight/altitude?

Altitude 38000ft.

Weight was 180000 kg. Not MTOW

Do you know what the percentage was of the weight? Should only be at 38000 at 21-30%

Edit: so works out 42% so optimal altitude is 36000 (source). I think the A339 might be one of the models with underpowered engines so might be the reason it struggled.