Why are parts changing dimensions?

:angry::cryin::crazy:

For some reason my parts coming off of my machine are changing dimensions while in auto mode running the same program.
I have not changed anything in the program. one part comes out fine then the next is off in x and z dimensions. for instance one part came out correct .615 dia and all the features in z correct the next part was .04 larger in dia and groves were off in z direction. I shut off the machine came back and it cut one part correctly but the second part was off by a different amount. This is a small production run and no changes are being made to the program.

I am not sure if it matters but this machine has scale feedback.

I have no explanation. This is on a Integrex 200sy 640mt control that is driving me crazy. I had the control replaced and it took months to get it back up and running however nothing operates as it did before. I have had other weird problems such as soft keys missing at certain times, machine shut down and restart on its own, random tool indexing problems and some of my options do notwork any more.