No lost steps, but wrong cut

I posted this on the Vetric forumn, but no one there seems to have an ideas.

I ran a 2 sided job that I have run before successfully. This time, the first side had mistakes in the routing(didn’t notice until later), but the 2nd side cut was perfect. To me, this means I didn’t have lost steps, but the Gcode was not executed correctly for some reason?
I can’t figure it out? Why would my GCode not run properly if there were no missed steps?
Any ideas?

Well, I can assure you it’s not the g-code interpreter.

You are overlooking something. Think about this, the most important number cited for the performance of your machine is the “repeatability” value.

It should repeat precisely each and every time within that 0.002" window. If it didn’t, check the workholding and re-home between every run until you figure out what the variable is. Also check if the tool is tight.

Also, check the tensioner bolt that keeps the pinion against the rack. Sometimes the threads get caught an don’t move freely up and down.

You can press down on the motors and lift the pinion off the rack. When you release the pressure it should returned to engage the track.

Check the wear in the pinion gears. Check linear rails for contamination. Somebody not that long ago found resin in his, messed up his bearings.