A few things to check,
- The wrong sized rails were used, check the text on your braces and actually measure your rails’ diameter.
- The two lower tension bolts on your core are not all the way tight, usually they are almost all the way loose. The core probably rolls real gritty in this case as well
- Check to see if you split your core in the center overtightening the tool mounts.
- Last print a tall 100mm+test print and check your Z dimension and you XZ & YZ tilt. Printables, or Printer tests and calibration