Gotcha. If it looks like the whole design moved slightly one direction, then you probably have lost steps. Lost stepper steps happen when the stepper wants to move but can't for some reason or other. A few common causes are tight V-wheels, loose/tight belts, incorrect potentiometer settings, and loose pulley screws. There's a good forum thread that addresses the issue that you may want to check out: https://discuss.inventables.com/t/guide-offset-cutting-lost-steps-positioning-errors-etc/16084
There's also a thread with some videos I've made that show how I check my belt tension and set my pots: https://discuss.inventables.com/t/x-carve-maintenance-troubleshooting-videos-add-your-own/13405
If that is only happening on one side of a cut along an axis (i.e. not all the way around), it may be an indication that your wasteboard isn't square to the spindle. Basically, the bit is cutting into the wood at an angle instead of cutting at 90 degrees.
It's also possible that you're just trying to cut too fast and/or deep and your bit is deflecting. If you think you have your machine dialed in, then try dropping your feed/speed a bit and see if the problem continues.
That should help you get started, lost steps and non-squareness are common problems with new machines. Once you get your machine dialed in, they will generally disappear.