I had a constant adjustment kinda thing going on with mine. Either the v wheels were too tight (after tightening to remove the wiggle) and caused lost steps, or I had the wiggle if the wheels were slackened to where they should be.
In the end I bit the bullet and replaced the Z. If I was just using the xcarve as a strictly hobby machine it may have been fine for that, but constant problems with it were costing me time and money.
To me the Z wheels sit too far from the spindle mount plate. Those four independent bolts are where my wiggle came from.
To be honest I also had a similar (albeit smaller) wiggle in the x carriage, but have since replaced the eight wheel bolts with 4 threaded rods/solid axles.