the wrong grease was used in the gear that froze up en route.
I've
had that on the TB20. Pitch trim froze solid at FL140. 1st flight after the Annual. The MO denied putting anything in there.
That issue is actually quite common. I know of a Citation which froze in the climb and was thus flown all the way to Spain with a suitcase jammed between a man in the RHS and the yoke, for a few hours
He was lucky he had someone else around to insert and remove the suitcase.