OAP - the nut at the duplex bearing end was clearly overtightened - hence my comment about assembly problems. It may be that the TR pitch change mechanism has to be taken apart and greased regularly which ,might make the over-tightening a servicing error instead.
If the nut is over-tightened and impinges on the duplex bearing, you have a probable cause for the excess heat and seizing of the bearing.
As I understand it the over tightening of the nut at the spider end of the shaft was likely caused by rotation of the shaft as the duplex bearing got tighter, not necessarily by over torquing during assembly. In other words the over tightening was a result, rather than a cause of the duplex bearing failure