Lift Assist Question

[sconcidine]

I recently purchased a lift assist for my 510. After installing, I find that the headstock will not slide past the half way point on the tubes. If I detach the gas cylinder, the headstock slides freely. When the headstock is in the drill press position, it slides freely even with the gas cylinder attached. It seems that the tubes are out of alignment when they are locked down in the horizontal position and the cylinder is attached. Anyone had this problem? What's the cure?