Peter
I had that very thing in a Seneca Five twin awaiting clearance to Join CAS at FL120.
i was down at 3000 feet in very heavy intense rain got the clearance and started the climb trimming the aircraft for that climb.
Approaching FL120 I went to level and found large out of trim forces with a jammed trim wheel.
I soon worked out what had happened and there was no alternative but to come down to below the freezing level.
A quick chat with the controller and very uncomfortable out of trim forces in the descent soon had the problem solved.
I then climbed again this time with no problems and continued on my merry way.
The Grease packing in the Linkage is important and it has to be the right type.
Pace