I'm wondering how complex your first "3D" carvings were? There is a not-uncommon problem where the polarity of the "direction" pulse is reversed. The effect is to lose one step every time there is a direction change on that axis. If there aren't many direction changes it might not show at all but where there are many changes you see exactly this effect. With a commercial machine this should all be set up correctly - but I've met one Chinese machine where the target for a proximity switch was a broken tap. And it would have worked fine except that it hadn't been adjusted correctly even though it did have a correctly fitted locknut! So you can't take anything for granted until proven. Slipping coupler or similar has to be the first place to look - mechanical issues are the most likely if it was working fine - but the dir signal polarity thing is not impossible and very easy to fix.

But if this is a repeat of a carving that has already worked fine a couple of times, then forget I said anything!