May be an idea to contact Dave at Hobby CNC to get the instructions on how it is measured (location of test point) and setting up the stepper drive current. I am guessing that if you can increase the motor torque it should solve your problem.
In my book you do not need lube on the screws with delrin nuts (the wood dust sticks to the lube and it just makes things worse).
Tweakie.
I know how to adjust the current on the board. It's at the Potentiometers. The label on the steppers says 3A, which is 3 amps. Should I have the board adjusted for 3 amps then ? The pots is where you adjust the board current. By increasing the voltage to .42VDC at the pots, the instructions say will give you 3 amps.