Go to motor tuning, and keep reducing the speed of each axis until reliable.
Start with low acceleration and fix that last.
Find the speed where moving cause it to not respond properly, then reduce setting by 20% or so.
You can use arrow keys (up/down I think it was) while in the tuning page to do the moving backwards and forwards.
Make sure you select save, before you try to do the movement testing.
Once each axis is reliable, for each axis, increase the acceleration until changing direction causes errors, and back off setting by 20-25%.
Each axis often has different settings.
Setting the machine up before trying to use it will save some cutters.
Follow the procedures in the Mach3 manual.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.