Lashout 24-volt throttle/controller problem

I have a LashOut electric bicycle, 24-volts, about 3 years old. Like it fine, but am having trouble with (A) throttle, (B) controller, or (C) something else? Symptoms. When I turn it on for the first time, perched on its motorcycle-style stand, the motor drives the back wheel very slowly without my pressing on the thumb lever at all. It will accelerate to full speed if I press down, and if I kick it off the stand it has full power - although it will not stop without being put back up on the stand, wheel still turning. Then I turn it off, and turn it on again right away, and now the motor will not run at all, even when the throttle is depressed. Any insights into what my problem is, how I might troubleshoot it, or how I might fix it? Much obliged!