TMZ 50/30 Swing help

I have a 2002 TMZ 50/30 towed aerial lift by Genie. Serial No. T5002-194
The problem I have is with the rotation of the lift. With battery power and using ground control swing moves freely and without problems, hydraulic pressure tested at 2800, if I use engine power and ground controls the swing will attempt to start and then stop moving, but I can push the boom by hand so the brake is releasing. Hydraulic pressure reading less than 1000 only on rotation.

All the boom functions work great on engine and battery power, no speed difference or anything out of the norm. Accept the rotation.
I have studied the hydraulic and electrical schematics and I am bamboozled.
Machine has updated Blue boards. And I get the same result from basket controls.

Any Help would be greatly received.
Thanks

Swing brake releasing?

Yes. I can move the boom freely by pushing the end both directions, as long as someone holds the button, I have taken the pump and brake off and inspected. I initially thought the motor had blow by and was expecting the pressure to drop, but I found it held 2800 on electric pump and never built anything over 1000 on gas powered, but only at the swing, all the other ports I tested was equal pressure. I am suspecting the valve in the manifold, however why would it only affect when powered by gas. The valve part from Genie said 4 position 3 way. Is there a way to test this? Im thinking someone may have switched it out, but there is no markings on any of the valves to truly know where they belong.

Thanks
Paul