Still having problems.

Hi, I am still having problems trying to set up my lathe. After getting a lot of help on this forum I am getting closer to sorting the problem out ( I hope ) first, I am trying to dial in the motor steps into mach3. After doing the sums, it works out at 1000 steps. I set the motor to this adjust the speed etc. save. Enter the command G0 Z+40, the machine moves 45mm so 5 mm over. Reduce the number of steps to 900. Input the command G0 Z+40 and the machine moves 60mm. Up the steps to 1200 and the machine moves 15mm. This is a closed loop motor. Can anyone please let me know what is going on. Also a few times the motor has not moved at all, until I de powered and started again. Could this be a breakout board problem, it’s just a cheap item off eBay. Thanks