Well, the shifter appears to be working fine. It's just a dumb device, no brains/electronics, just a coil of wire. Current through the coil creates a magnetic field that pulls the shifter cam up. Stop the current and a spring sends the cam back down. The inverter is switching the current on/off when it shouldn't be. The inverter has it's own microprocessor (brains) and program algorithms. I don't think the control panel could be making the inverter do this. Sounds like a bad inverter. Are their any error codes on the inverter? Three flashes = corrupted software. If there's an error code, try resetting. If not, replace inverter/motor.