I had an issue with both the X and Z when I tried to move them the first time.
First I checked that I didn't have the V-Wheels too tight. But still had issues.
Then I realized I needed to check the motor drivers power. I had skipped over this part when building my X-Controller.
Once I set the trim pots for the NEMA 23s they worked well and I did my first carve last night.
So like @eried said, check y our trim pots on your motor drivers.