I tested the @sorceress map
I think it is possibly slightly broken?
Did you test with Chocolate Doom?
The very first door refused to open, until I modified the sector slightly in Doom Builder 2 (see pics).
At the very end, after opening the exit door but before pushing the exit switch, I got a hall of mirrors effect.
At the start, the map was a bit short on shotgun ammo.
Here is a demo, I accidentally played on HMP:
https://drive.google.com/file/d/1mFU2VZ5Jg5o_brhuw-lALZwxHNyjh_Gn/view?usp=sharing