Sometimes the maze generation runs into a dead end sooner than expected and maze rooms fill the level.
Strangely this one can be navigated, but since doors are placed on a random wall (one per room) it's also generating room areas that are not connected to the level. The way rooms are created in the maze is actually nice, even if they take a lot of space, but they should work as a part of maze or be a maze of rooms itself. How it's done, I don't know yet. You could place doors to each wall, but then it's not very good as maze.
If everything else fails, I should keep rooms attached to maze level and skip rooms that would be created next to another room.