When standing on a staircase block that retracts into another staircase block, the game teleports you around 40 blocks away from where you are standing, and sometimes you just completely phase through blocks behind it into the floor.

Observed Result: When standing on or near the staircase block you will either teleport far away from where you are standing or phase through the blocks.

Expected Result: When standing near the staircase nothing happens. When standing on the staircase you don't phase through the wall.