I just bought a Harig 618 Automatic Surface Grinder. The problem I am having is that the longitudinal table will not reverse. I have tried manually moving the table reversing lever and nothing happens. Is it possible that the reversing valve is 90' or 180' off? I am running this grinder on a VFD, the VFD will shut off due to what I think is overpressure from the hydraulic pump. The grinder was recently moved before I bought it. Any thoughts?