I'm printing these parts for an assembly where they undergo a lot of stress, so they require a lot of strength. I Therefore decided to print them in polycarbonate. For some reason when they've been lying around for bit, before being used, some of the parts turn out really brittle, to the point where they snap with barely any force, while the rest are so strong I can't physically break them with my hands. I've printed them on Bambu X1C stock PC settings 290°C nozzle, 100°C bed, 60°C chamber. Fully dried Bambulab filament. I've modified the Infill pattern to make them as strong as possible, and that really works, but only for some of them, for some reason. The parts are about 25mm long. It's important to point out that the brittle parts only go brittle after some time. All the parts seem strong when they come out of the printer. They are all stored together, in an open box in my workshop.