I'm going to assume you have the steps per setting because without this being correct your wasting your time doing anything else.

Which vectric software is it.? I've recently noticed some of their lower-end products have a limit on cut size. Could it be this.?

Does it repeatably cut the wrong size or is the size random.? if it's random then check your motor couplings etc haven't come lose and your getting slippage. You need to establish that it repeatably gets it wrong before changing settings as it could be mechanical.