spindle movement, unround holes

[bbortnick]

Hi,
Wondering about some things (related?) with our shopbot prsalpha 48x48.
1) Small holes made with profile CUT are slightly oblong and therefore one dimension is a little smaller than the requested dimension.
2) When changing bits in the middle of a file, it's very easy to move the spindle, loosing your x/y position. I can reset with proximity locations, but if x/y was elsewhere, it's very hard to restore to that spot.

Everything seems tight on the gantry, but is the most likely cause of oblong holes worn pinion gears?
Is there a method to changing the bits in the middle of a file that does not risk moving the spindle and loosing your x/y?
Thanks for the help!