Mark,
Given all the obvious fault finding there is another scenario that may apply here.
I have seen an RV10 elevator trim fail in a full UP position
it can also fail in full DOWN as yours appears to have done.
The failure I’ve seen still will have the aftermarket relays (if fitted) working, however reversing the wires will not necessarily make the trim motor work in the opposite direction.
The trim motor is a Ray Allen unit with inbuilt limit switches and operates the trim tabs via a bellcrank & cables. Most other RVs have a direct drive setup.
In all cases you can drive the trim motors to their limits with the limit switches normally doing the limiting of travel.
IF the cables/bellcrank travel is not adjusted correctly at installation then you will have a failure like you describe, it’s just a matter of time. What can happen is you drive it fully one way & , because the travel is incorrectly set up, the limit switch does not cut out the motor which is then continuing to load up the gears.
Do this once too often & the gears get stripped & (maybe jammed) the motor is in ‘neutral’ , not doing any driving. I have seen this happen in a full UP position.
IF the other simple checks don’t work then I’d remove the motor, unscrew the motor cover & carefully check the gears as the damage is hard to see.
The simplest fix is to replace the unit - make sure the trim system is adjusted properly.
HTH,
Jake Jansen ( Jake J)