Usually a stepped appearance is caused by lost steps.
Per the machine operating checklist: Machine operating checklist , the basic points of adjustment for a machine are:
- Pulley set screws — verify that these are in-place and secure — for further details on checking them on a Shapeoko 3 see: http://docs.carbide3d.com/shapeoko-faq/shapeoko-3-how-to-check-the-pulley-set-screws/ — be sure to check all axes/pulleys (including Z on machines w/ belt-drive Z-axis, for an HDZ, check both coupler screws).
- (for the SO3/4, X- and Y-axes) V wheels / eccentric nuts: Tightening Eccentric Nuts - Carbide 3D
- (for the Pro, and SO4 Z-axis) Lubrication of the linear rails: Getting Started with Carbide Machines
- Belt tension (see the relevant step in your instruction manual, e.g., Getting Started with Carbide Machines) 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
A good video overview on setup:
Ensure that all screws are in place and secure, esp. on the linear rails on a Pro.