managing a legacy an Group

I totally feel this - wasted so much time and plastic on a mech that looked fine on screen but printed like a tangled mess of supports. The first real wake-up call came when I finally understood how many "watertight" stl files for 3d printing actually have hidden holes or reversed faces that your slicer won't fix automatically. From my own fails, I now always check for crazy thin walls (under 0.8mm for mechanical parts), overlapping vertices, and any floating geometry that isn't physically connected. Another huge red flag is if the model was clearly ripped from a game without being remade for printing — game engines love single-sided polygons and zero thickness capes, which are pure nightmare fuel on a build plate. I've learned that if the file loads but refuses to slice cleanly, or your preview shows random missing layers, just trust the red flags and move on.