First discovered by IbxToycat in his video on lobby secrets.
While wearing the elytra open the piston door to the nether area. Stand on the blocks that just retracted, the row inside from the stone blocks in the walls.
Rapidy hit X on PS4r, A on XBox to activate elytra while jumping and you will glitch through the floor.
I then brought another player in and played, on returning to the lobby iwent back the the nether area to find all the pistons and blocks attached to them were now missing.
I also found that flicking the lever a couple of times results in the blocks attached to the pistons disappearing. The top and bottom pistons can be seen but don't operate despite the piston sounds. The side pistons have vanished.
Try any above without the elytra and nothing weird happens.
I cant get this to happen with the piston door to the water area so something specific to the nether area door??
See also MCCE-4407