Front electric jacks

I have a 3670RL that we have had for three years. I had the motor for the front jacks replaced and it worked twice and I am having problems again. The motor turns but the jacks do not go up. I emptied the basement to make sure I was not over loaded.I took the pressure off the unit with a hydraulic jack and connected to my truck. I put all the stuff back in the basement and went to our destination. When we got there, the unit lifted off the truck with the stuff in the basement. This has happened three times. I do not know what the problem is. Any suggestions? How can I find out if the correct motor was installed? Thanks, David <><