Player can fall into solid block

Somewhat randomly when I am moving quickly (not "running") up the stairs in the picture I will fall into a solid grass block. Occasionally I will fall in 2 blocks and take damage until I jump out. It might possibly be affected by a (wood) pressure plate deactivating and closing a door behind me at about the same time as I reach the block I fall into. I would be willing to run some test cases on a backup world if helpful.