Re: Need some help, Machine not carving straight lines
If you look at the drawing I posted earlier there is a spacer labelled #4. There is also a spacer pushing on the inner bearing races from the other side, and I believe that's the most common arrangement. The second spacer is probably not labelled because a screw can be machined to serve the same purpose as the second spacer but I believe this is less common..
Disassemble so your just left with screw, bearings and spacer(s). Now when the nut is tightened the bearings shouldn't slide side-to-side. If they do slide the reason is most likely a damaged or missing spacer.
If it passes that test place just the bearings in the housing and check if the retainer is preventing the bearings from sliding.
As far as replacing it, google "BK ball screw support" and find what matches in dimensions. If it's better quality the housing may have an identifying stamp. If you find the bearings inside are regular deep-groove it's probably generic China. If the bearings are angular contact it could be name brand or at least better quality generic China.
Anyone who says "It only goes together one way" has no imagination.