My machine was running great for awhile (thanks to folks helping on here)

But now it a couple of times did not return to zero after a job. I noticed this once, then did an inlay (male and female) the pieces did not fit as they normally do but the machine did return to zero both pieces.  Then I did a sign and while the sign turned out , the machine did not return to zero after finished...

I am still very "green" with cnc machines and especially the major programming stuff...  Any clue what would cause this or how to tweak it back to when it was running perfect?

TIA

What kind of machine is this? You need to check all the moving components for binding. Lubricate if necessary.
If that doesn't help, you may need to lower your accel and velocity in motor tuning.

Thanks Gerry,

I really trust my motor settings because Tweakster and RobertSparks helped me and the machine has been running great ever since...  ( a couple of months)..

This is a Romaxx WD-1 machine.. Uses stepper motors and ballscrew... 

It is a newer machine and I am a newbie to this stuff.. What lubrication is best for areas of moving parts?

Thanks,

You need to grease the ballscrew regularly (but not too much).
I'd ask Romaxx what they recommend.