HI guys. I've had a 4x8 Chinese machine for about 3 years now. I do a lot of 2d cutting and everything is spot on in that aspect. The only glitch is when I do 3d carving. I'll start a 3d carve and rough out and then start a finish pass. As the finish goes along the Z slowly rises to the point within 15 min into the cut it's no longer in contact with the model. The z is tight as well as the new belt. The bit isn't slipping and the collet is new. Everything is lubed as it should be and there is no binding. My thought was EMI but I've done everything possible i believe to assure that wasn't happening. Just replaced the spindle wiring with a foil and braided cable as well. It has an XHC controller running Mach 3 and seem to run great just till I get into the 3d and Z motion. Any input would be greatly appreciated.As always thank you in advance.