What sort of toolpath are you cutting?
If your machine is mechanically sound (pulleys secure, belts well-tensioned, linear rails lubricated), check the wiring.
You can verify the electronics by powering down, removing both Y-axis belts (label them so that you can swap them side-for-side and end-for-end), and putting a bit of tape on the pulleys.
Then, power up and connect to the machine and try to initialize — the ma machine will home Z and X as normal, while the Y-axis should turn until it times out — do the two pulleys turn evenly and in synch?
Let us know at support@carbide3d.com