Door Glitch(MCPE)- affected all versions since 1.18

This glitch allow all entities – players, mobs, and non-mob entities to stand inside a closed door, trapdoor, or fence gate (any wood type). The player/entity does not suffocate, and once the player/entity moves out of the closed door block by jumping or moving forward, the closed block acts tangible again. While inside the door block, the player can not interact with other blocks, only the door block itself. For trapdoors or doors, this works in the opened form as well. Players can exploit this glitch by making stuff like trapdoor elevators. 

To replicate:

Place a door block.

Open it.

Stand where the door block will close.

close it.

You will be able to move through it.

Trapdoors:

Place two vertical blocks.

Place a block next to the bottom block.

Place a trapdoor on the upper side of the top block.

Open the trapdoor.

Stand on the block beneath the trapdoor.

Close the trapdoor.

You can move through the block.