Common beginner problem. The natural tendency when you go air born is to face your body fowards, which will cause you to turn in the air and land on your ass. Keep your shoulder parallel to the board. A simple grab will force you keep your shoulders properly aligned.
I'm comfortable enough to do a grab, I just thought I should sort out my basic air issue first. Though maybe not.
I will say that it does happen occasionally with a grab as well.
It's sort of become a mental issue now that is screwing with me on approach. It's hard to get comfortable.