Loosing steps. Check Pots, pullys, belts
Ya, I agree with you. I had the same pattern and my pully lost it’s grub screw.
This is almost always the culprit of behaviour like that. Loctite those suckers
I have noticed that when I start to carve the motor on the z drive start to shudder and it never done that before.
Are you running an arduino and gshield? If so did you go through the process of adjusting the motor potentiometers?
I found my Z axis needed adjusted far higher than either X or Y
Yes I done that today ,and running Arduino and gshield, I though it might be Arduino or the gshield playing up.
Check your pulley set screws. At least one either came out or are loose. Use blue loctite.
Before you start thinking about throwing the machine out the window, check out in here the xcarve. mod pack 1. Especially replacing those tiny set screws and the one for the eccentric nuts. Those are the 2 major ones that I think that are a pain in the machine if you don’t do them. It will save you a lot of time trying to adjust your machine after every other job. Do as many upgrades as you can in your machine and you will have a descent cnc. Good luck!