Genie S85

I have a 2000 Genie S-85 dual fuel gas/propane 4x4. It got loaded on a lowboy and brought to a job and unloaded. The next day my guys went to start and when trying to start it would try but just wouldn't fire. When it would try fire the machine would start moving forward. once we took the hydraulic pump off from the motor it started and ran flawless. Put pump back on and no start. After bringing a Genie dealer mechanic out and another mobile mechanic ive replaced the the primary and secondary pumps. Even after that machine did same thing!! Everyone i talked to is stumped from Genie dealer, second mobile mechanic, and genie techs when you call them. Managed to get machine loaded on lowboy and hauled home. When one of my guys went to unload it, its started and walked off the trailer but didn't walk good. Machine was thrusting. Shut it down and at a later date one of my guys with another mechanic friend looked at it and while running it blew out seals on drive motors. Replaced drive motors and upon start up blew out new drive motor gaskets. Resealed the motors and machine does not drive right. It will not drive up a hill you can hardly get a basketball to roll down and when it cuts out and you let off drive control now brakes wont set up like before and it will try roll. After all work auxiliary pump doesn't work like before all the work. Now today months later of endless headaches and stumped mechanics it still wont drive and seems like possibly stuck valve or ???? Today the hydraulics got so hot on one of my guys working on it you could cook your morning eggs. Anyone with any ideas please help!!