It seems like it happens after the second step of a multiple automatic thing, like,
1. I make a move
2. some pieces clear
3. more pieces appear
4. those pieces clear
5. now I can move the cursor and move pieces
6. the pieces that should have appeared after step 4, appear, but I'm already moving around and changing things
I'm trying to avoid doing this for now because I'm in the middle of a nice run, but if I wind up game-overing I'll start a run just for fun and see if I can get video or something