1)how old is your machine and are you the first owner?
2)is this a recent problem?
3) is the machine under warranty?
check to make certain that the linear bearings that the gantry rides on are straight. 2 check the angle of the gantry to the bearings. I have encountered instances where a gantry took a hit during shipping or some where else along the way and was knocked out of square. I think techno has a protocol for re-squaring the table, give them a call or check their on line files.