Summoning a falling block with the texture of a stair with "/summon minecraft:falling_block 136.5 64.5 237.25 {BlockState:

,Time:100}" in the empty corner of a stair block will destroy both the falling block and the stair, and leave behind a glitchy area that you can't enter but that has no contents. Upon relogging you will find that at least one of the blocks are still there, ocassionally both, with the falling block on top of the original. This does not seem to happen with other BlockStates in the same coordinates, as the falling block will instead just be destroyed.

This happened in creative, survival and adventure mode.

To recreate, place a stair and record it's coordinates, then summon a fallingblock (with the same blockstate as the stair you placed) on the lower step. this can also be achieved by summoning a fallingblock at the player's feet when they stand on it.