The locked doors to the tower found by going west of the main town (with the museum, bank etc.) are intended to check if players have the right keys and disappear if they do.
These doors do not loop properly, causing them to be unable to be opened if you don't already have all the keys (four white, one yellow, and not standard ZZT keys) when you first enter the board.
If players specifically avoid visiting this board until they have the keys, they can get past as intended. Otherwise, cheating becomes mandatory.
(Report entered by Dr. Dos, original report by Zinfandel)