Dealt with this all the time. Started using a torque driver on every heating element screw. Set it to the manufacturer's spec. Callbacks dropped big time.
Emma's torque driver idea is the real game changer... it takes the guesswork out completely. I used to just go by feel, and sometimes I'd over-tighten and strip the threads. Following the actual spec sheet stops you from causing a whole new problem while fixing the old one. It's a small extra step that saves so much headache later. My boss even bought a couple for the shop after we kept having the same callbacks.