Driving me insane

[Bush Flyer]

Yes it's always the same axis that goes wrong X and A axis slaved. One stepper motor stops and the other keeps on going. I did a small line picture the other day and it started fine then half way through the cut it moved the rear part of the picture 12mm away from the front part. It will run fine and I even rerun a g-code today 11 times over the same picture and it will follow the same line spot on, then for no reason on the 12th time it will go and cut a line short and mess it up.
The first time I really noticed it was when I first fitted a spindle and VFD in place of the router, Also when I first switched on the machine and seen it move for the first time, it did crash in to the limit switch for no reason I was jogging the x axis then it didn't stop but it's been OK till the spindle was fitted, Having said that I have seen it go funny with out the spindle running, on just a test run no end mill fitted.
If I lower the acceleration down to 200 will this cause a problem if I try it at this setting for a few days.
I have got to try something.
When it goes wrong the g-code stops in it's tracks along with the machine and then carries on but not in the right place or one of the X or A stepper motors takes a extra second before moving with the other one.

[JAZZCNC]

When it goes wrong the g-code stops in it's tracks along with the machine and then carries on but not in the right place or one of the X or A stepper motors takes a extra second before moving with the other one.

Ok this needs explaining better.? When you say the G-code Stops plus Machine then it carrys on do you mean it pause's for a second then continues.?

If so then this is indicates a computer problem and Something is interupting Mach. If this is the case then don't do anything else to wiring or Mach setup untill you've fixed the Computer. Mach cannot be interupted for even a split second otherwise it will cause lost timings in the pulse train and you'll get exactly what your getting.

Remove any virus checkers, Disconnect from internet and turnoff any wireless, Turnoff screen savers and Energy saving features, Remove Apple Quick time or Adobe products as they cause interupts.
Infact remove any programs that you don't need.

You need a very basic stripped down windows with just Mach on it.