I have been having an issue with the mast going all the way forward by its-self with no load on the forks. When trying to tilt back the engine bogs down and I have to rev the engine up to get the mast to tilt back at all. I had both of the tilt cylinders rebuilt which fixed the problem for a few weeks. I went to tilt the forks all the way forward and then the same problem came back. Then i replaced the valve that controls the lift and tilt cylinders with a brand new one. It looks like one tilt cylinder may be working somewhat and the other one is not. They also seem to be a bit out of adjustment. when tilted all the way back one cylinder goes in about 1/2" farther than the other. This is the cylinder that appears to still be somewhat working. The hydraulic fluid is fairly new and the tank is full. There are no obvious major leaks anywhere in the hydraulic system. Most of the hydraulic lines have been replaced. Does anyone have any idea of what could possibly be wrong? Any troubleshooting help would be greatly appreciated