In my opinion, the design looks good but not the best for FDM printing. You could incorporate a lot of supports or re-design it to print separate parts and then assemble them with clue or/and fasteners.
One, did you check the STL file for manifold issues? If yes how did they being tackled?
Two, what slicer, what settings were used, for what filament, and in reality what filament was used to print. Nope, PLA does not equal PLA, you take a new spool, you have new problems, first one has to verify the printability of each new spool (or used spool if sat for days in a row in the environment, PLA absobs humidity, gets brittel for sitting in the sun, etc, PETG is worse with humidity, not to mention nylon, Polycarbonate or ABS)
Dd your client chencked the filament by print testing it in 5C temperature incements for printability?
Having a 3d PRINTER IS ONE THING, KNOWING WHAT YOU ARE DOING, WELL... just about another kind of thing.