I have a Trek with press fit BB bearings. It has only been used occasionally this last year so has sat for a while between uses with no apparent problem until now.

Last week when I set off the crank would barely turn. The movement was smooth so not like rusty or dirty bearings. A quick squirt of GT 85 behind the nearside crank immediately cured it and when I took the cranks off at home it was clear that the GT could not have reached the bearing due to the plastic top hat spacer and both bearings felt OK. Removal of the top hat to inspect the bearing would have destroyed the spacer. I assume it is a sealed bearing and the bike has not been near a pressure washer. It was fine next time out but is now again like trying to turn through thick treacle.

Any ideas?