If you are having caps fail on a regular basis on the same motor you need to investigate the power quality of the circuit that supplies the power to it. AND run a megger on the motor.
Oh, maybe I should clarify! This is not a repeat problem with the same motor. I was talking about cap failures in many different electric motors, over the last 45 years or so. It appears to me the motor mfgr’s often skimp on the caps, relative to the rest of the motor.
You are of course 100% correct about the other checks — all looks great.