I'm fairly confident that it's not an electrical issue as part of the trouble shooting we've replaced wire and connectors.  Voltage is good in all phases.  

O-rings.....OK - i need to revisit this but maybe 1 is bad or we missed one which is letting flow by when it should be holding.  Can't remember if we pulled all the fittings and recheck them or not (we've had those things in and out so many times i lost count while troubleshooting) but sometimes you need to start from ground zero like you've done nothing.

Yes on tractor.  Only tractor it's ever been on with our farm.  Flows are set correctly and hoses hooked up correctly.