If a zombie begins to break a door and the zombie is killed before the door is fully broken, the damage will stay at the percentage it was at when the zombie died. It will remain if the door's state is changed, or even if the door is removed and replaced with another block.
Related issues
Comments
kumasasa
migrated
It's not a regression, MC-1 was never actually fixed. Mojang simply made the door damage reset after 20 seconds and marked it as fixed. I would like it if they actually fixed the problem, but it seems clear they won't. This ticket should probably be resolved as a duplicate.
Regression of MC-1 ? Yes, MC-ONE