I doubt that the failure of the duplex bearing made much vibration, the TR servo end (non-rotating) would then be pushing on the TR spider shaft end (rotating) and that would be the only source of vibration. The duplex bearing is greased, but if oil leaked somehow into the shaft area (split O ring?) the oil would soften the grease and heat could destroy the bearing.
The TR would then be able to be pushed to higher pitch by the stupm end of the shaft to get more left pedal, but could not be pulled to lower pitch (right pedal). This is possibly what happened.
HUMS is great, but it can't see everything.