One other thought you might want to try and this involves jacking unit up and blocking unit to get drive tires off ground. Remove floor board and check if your motor brushes for drive tires ( 2 ) are good and not arching. they are a pain as the motors are stack one on top of other.Sometimes they will not make commutator contact and drop contactors out. Batteries are a problem also as you are not getting but only 5 minutes run time and will travel no faster than walking speed. Best to also get steer tire off ground and run lift while turning left and right. When turning right while sitting on lift, the right drive tire should slow down and at almost lock, it should turn backwards. Same is true when turning left.....left should slow and at lock turn backwards. As i said check yer brushes and let me know what you find out.