Rocking the lift? Sounds like a dead spot in a Traction motor. Maybe worn brushes or shorting motor. Waves are known for the motors to go bad and usually putting the truck in "push" then pushing it a couple inches, then drive and it working is a common. Let me know what you found or if it's still a problem. Code 24 (the 2 middle bars blinking) refers to left motor open at start up.