Whenever a door is surrounded by tiles of the same resource used to construct the door, it will delete the resource it was made from—special cases for pneumatic doors where it deletes anything it is embodied in but loses its resource when it is in the same ore. I found this while testing the conditions for making a natural tile using manual and mechanized airlocks, with @hydrotoast and @kurosolo. There is a strong relationship for it to have to do with maxMass property. It is the same condition that is satisfied for making natural tile, then it will cause the deletion to occurred if the tile side is surrounded by 8 sides of same material, this includes from metal, bunker, and storage tiles. The condition is stated by Mass drop + Material Cost of Airlock/Tile occupied < maxMass. Aluminum is a special case for not deleting. Sorry for sounding like a report, just my observations. Hydrotoast states that it is similar to this previous bug that was quickly patched:
1. Surround doors by the same ore it is in.
2. Deconstruct the door
3. Resource loss.