It sounds like pretty typical over-stressing at the base of the snap feature. Even though PA12 is flexible, with 1.8 mm wall thickness and a 1.5 mm deflection, you’re probably exceeding the elastic limit locally—especially at that sharp corner where stress concentrates. Despite good toughness, the particle welded microstructure isn’t forgiving for sharp flex points in the way molded parts would be. A few cycles of flexing plus small layer inconsistencies can easily initiate a crack.

You might want to increase the wall thickness around the base to 2.5 mm or more if you can afford the space. Also, think about adding a small radius fillet where the hook meets the wall—like at least 0.5 mm. It’ll spread out the stress a lot better.

You could tweak the hook geometry to work better, but this is actually a solved problem— a thinner, longer arm that flexes more uniformly would survive better, but existing solutions look different.

Take a look at standard PCB mount hook types, they offer a more forgiving approach. It takes the stress away from the base and spreads it out.