Then 2nd jeff & karen sign then tried 3d i did not zero out the clip art but i do not think that is the problem. This is my 1st 3d art… IS this mechanical
seems like you have some slippage in the “Z” assembly or v wheels need some adjusting.
possibly on your “Y” axis due to the fact it comes and goes.
Thanks ken i will check it out all z axis and every thing else. Another site suggested EFI issue
Looks mechanical to me.
Check your v wheels
Not likely an emi issue.
Ok, this might be the culprit >> some of them have come loose.
thread lock helps.
I will take a look at that 
thanks so much. 
I will give it a go over whole machine tommorrow
It’s actually the coupler that’s hidden and only accessible from the backside hidden behind this bracket (red arrow) that’s the usual issue.
BUT I really wouldn’t expect the z to drop for the center like that only, and then recover and go back to a higher location from a loose coupler.
@JeffWilliams2
Is it possible that the bit is loose and moving around loose in the collet mid-job?
And also make sure the Z axis isn’t mounted too high, I doubt that’s related, but a lot of the owners of the new Z tend to mount it up too high and then their shorter length bits cannot reach low enough for some cuts.
