I found this floating around in cyberspace.
Looks like one side of solenoid has B+ (+48V) applied whenever Tow switch is in the operate position (or whatever it is called) and you have to have B+ on pins 1, 2, 3, 6 and either 4 or 5 to get controller to supply B- on pin-11 to activate solenoid.
When the cart is misbehaving, check for voltage (B+) at the solenoid coil and the pins listed above.
If you've got all of them and the solenoid isn't closing, my guess is that either the controller or solenoid is bad.
If you don't have any of them, the Tow switch is bad.
Since toggling the Tow switch is turning the controller off and on, resetting it, I'm leaning towards a bad controller. (If Tow switch is good)