Event sheets are read top to bottom, so if you use on start of layout then you need to make sure that your room is created before you look for overlaps to create a door. All events will be checked each tick (depends on your monitor rate, but usually 60 times per second) so if you don't have a trigger once or other limiting condition for something like this then your walls will be checked a lot... Also, because of the way that events work, you don't need the for-each loop as that selects each wall in turn and will create a door for each one that meets the or group criteria.
Yeah, that's what I figured.
So... remove the for each loop and move the overlap check (events at line 2) and put them after the create room events (line 7 / 8) under the on start of layout.
That doesn't work. Instead, not a single room is generated. I'm thinking it attempts to generate it, but unless I get very lucky and RNG lands on the 20 or so applicable squares out of 1,000 possible I wont be seeing it.