I have an issue with Mach3 that I am scratching my head about.  I went to calibrate the the motors, I hit 5 inches and it moves 5 inches.  Every axis good.  I load a test part to run and something goes haywire and the motor steps are off.  I go to the MDI screen and hit Y1 and the motors move about 15 inches.  I then go back into the settings page and hit 5 and it now moves 15". I just can't seem to get a repeatable result.  Why do the settings keep changing?  Thanks in advance for the help. 

Do you always press "Save axis" before exiting the settings screen??

No I hadn't  because I didn't change the dettimgs .  Do I need to regardless of i change something or not.
?

No, only if changing something

You are not set for metric and running inch g-code?

 I was wondering the same thing but on the settings tab when I say move five it moves 5 inches not millimeters. 

Is this setting correct?

Mine is the same as yours, set at mm.

and your GCode what does it look like.

G20/G21

GCode is in inches.

so if you set up mm and GCode is inches, what would you expect ?