I may be late to the party. But I had the same issue, I have a 40BX. Turned out to be a cracked/broken power connection to the motor. I"ve never seen plastic just crack like that. In any event, I carefully removed the wires from the broken plug, used some dialectic grease and some clear 100% silicon to correct. Not a lot of extra wires to mess around with. so far so good. I have had it "stick" but opening and closing the door couple of times worked. Also you can take and tap the motor with the handle of a hammer. Sometimes the gears inside over rotate and lock. It's really not a Thor issue as it is the manufacturer of the step...kwikee-steps..guess who...lippert..not impressed with thier products
https://www.lci1.com/kwikee-steps