I have got problems with my V2XT Z axis ball screw.I will try to condense the story. Z axis would only extend from about 1 to 2 inches, never in the same place. But between that approximate range. Couldn't jog, and the circuit board for the Z drive would flash a yellow LED. Switched the cards from Y to Z and no change. Wound up taking the ball screw out of the machine and taking it completely apart and reinstalling 299 balls. This was well lubricated and no mechanical damage. BTW the balls measure .121.Now when I hold the shaft vertical and spin the nut by hand it will spin real easy for about a turn and a half and then something happens the resistance gets a lot greater but it still turns. It almost seems like the balls are freewheeling and the get stacked against each other or something. Also tried to get some info about the NSK ball screw but couldn't find any thing. I'm kind of at a loss about what to do with this thing.