This is probably a mechanical issue, I’d suspect insufficient belt tension on the X-axis.
Per the machine operating checklist: Machine Operating Checklist - Carbide 3D , the basic points of adjustment for a machine are:
- Pulley set screws: Checking Pulley Set Screws - Carbide 3D — be sure to check all axes/pulleys including Z.
- V wheels / eccentric nuts: http://docs.carbide3d.com/support/tensioning-eccentrics
- Belt tension (see the relevant step in your instruction manual, e.g., Step 5 Belting - Carbide 3D) Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues. Also, belt tension for the Y-axis stepper motors needs to be even/equivalent on each side — a significant difference can cause skipping on one side eventually resulting in lost steps on both. Measuring belt tension, squaring and calibration