As Hood was asking - we need far more information to advise you what your problem might be.
1. Is your machine properly set up. are your steps per unit correct. is your motor tuning in respect of speed and acceleration at a speed where it performs reliably, and finally as Hood said - have you any backlash on your system, have you measured it, and is backlash compensation on.
2. What GCode are you trying to run. Is it a small program, or is it just an MDI line of commands.
3. To achieve repeatability, you must ensure that your machine is "homed", all offsets are reset, and your 0.0.0 position is the same each time you start.