What is your movement's setting, and is the game running at 60 fps?
Movement setting is at instantaneous. When I posted this, the game definitely wasn't running at 60 FPS. I've since started the Outskirts and changed the settings to have that run smoothly. The game now runs closer to 60 FPS and I didn't encounter any combat on stair spaces when repeatedly going up and down floors, even with monster lure active. I only tested the floor change about 15 times, but if it's just a processing speed issue I'll keep resolution low for the dungeon.