After we swaddle weaned and sleep trained LO, I started putting LO on her tummy in the crib, since she would flip over immediately when I put her down on her back. And she seemed to like sleeping on her tummy better. But recently, LO has been flipping to her back in the middle of the night and would start crying as if she's stuck.

Last night, she woke up in the middle of the night, flipped to her back, and fell back asleep after a little bit of crying (which is unheard of!) I just put her down tonight on her tummy again, and she immediately flipped to her back and started crying. 15 min later she is asleep on her back! Could this be a change in her sleep preference?

Did your LO's sleep position of choice change over time?