My first thought is that your batteries are low but that seems unlikely after some thought. I would be inclined to think that your motor s=assembly has some wear problems and or that the lift motor is failing. There isn't any adjustment other than the cams you mentioned.
If you disconnect the complete motor assembly and the steps move freely from fully extended to fully retracted by pushing on them, there is nothing left but the motor assembly. Without being there to see it, I would suggest matching up your lift motor with one from a motor parts store and try that. There are literally hundreds of threads maybe even thousands of them just on the Kwikee steps and the best thing is experience in repairing them to diagnose the problem.