In the epidsode when Joey builds a entertainment center he cuts Chandler's door which makes Chandler fall over it. Yet mysteriously in the next shot of them in the apartment the door is fixed again.
I know for sure that the door is still cut in episodes after that,I defiantly remember seeing the cut door in the episode where Joey has a snoring problem and Chandler goes into his room, the door is still cut....
The door always remains broken. If you recall Chander falls over it it the same episode and later on when Rachel and Emma are living with Joey you can always see the crack along it. its just been glued back together. As you would assume they would do, as Joey was a stuggling actor at the time!