invalid doors

[amitabha]

everytime I output my wad, a error message comes up saying invalid doors for room 0

[Titak]

Check room one for invalid doors. ;)

Sometimes doors (connections between two rooms) get corrupted, either because they are not placed correctly (rooms overlappign or somethign odd liek that) or because of something else.
It is best to delete the doors in room 0, then make sure the rooms you want to connect are lined up properly and then reconnect the rooms.