What is the 'Centrifugal Liftoff' failure mode, and how do you diagnose it in a failed high-speed motor?

Centrifugal liftoff occurs when the RPM of the shaft is so high that the centrifugal force $F_c = m r ω^2$ overcomes the elastic 'cling' force of the ring. The ring expands, leaves the groove, and is then destroyed by contact with the housing. Diagnosis involves looking for circular scoring marks on the inside of the housing and checking the ring for 'expansion' beyond its original free diameter. If the calculated limiting speed $V$ is less than the motor's peak RPM, the ring must be replaced with a 'Heavy Duty' series or a self-locking variant to ensure it remains seated at all times.