Can you tell us how the tool is mounted on the faceplate? Is the screw perpendicular to the faceplate? Is is parallel? Is it parallel and rotated? Also, is the robot itself level? Usually none of these scenarios pose much problem. but once in a while they do. It shouldn't be an issue if you are jogging in World in the X,Y,Z planes alone, but if you happen to be jogging in User in a frame that is not perfectly straight it could be.
Also, have you looked at your frame data to see how it looks? Is there data in the W,P, and R data? Menu-Setup-Frames-Type User, select the applicable frame you are having issue with and look at the data.
Sometimes, when touching off, your Z height is off a tiny bit and this will induce some angle into your frame. I have already manually adjusted the frame data and zero'd it out in a couple instances.