It looks to me as though the action of turning the isolator off is dropping out the raise contactor,so I'd guess it's a control issue (which I think we've worked out already!!!).
How does the lift work?motor up and down or does the motor power a hydraulic lift then it just releases the pressure to lower it?
My one was electric power,hold the button in then release wherever up and down.
A lot of them are very crude,literally the push button has a plastic stalk on the back that pushes the contactor in physically to operate it,usually interlocked then to prevent arcing if up and down are operated simultaneously. I'd go for jonboy's idea of a good physical clean up first,something sticking etc.