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If a certain block somehow finds its way into a position it should not realistically be in, such as on air, water, above a torch, etc., the block will continue to insist that it is in a valid position and will not break even if given a block update.

Blocks affected:

• Torches and wall torches
• Signs and wall signs
• Heads and wall heads
• Buttons
• Levers
• Pressure plates
• Doors
• Beds
• Banners
• Tripwire hooks
• Ladders

Rails, redstone dust, repeaters and comparators will pop off instantly when updated as one would expect.