I have a 1000x1000 X-carve. I have started using it more and more as the weather has been getting colder and the workshop is freezing. The last three carves have been horrible. If the roughing cut is good the finish cut is off completely. On the previous carve the roughing carve was off by 2 inches on half the carve breaking a bit and ruining yet another piece of material. Before every carve I tighten the same screws that always seem to come loose and check them throughout the carve. What else could be going wrong here? I am about to scrap the machine and get a better quality machine that doesn’t have pieces fall off mid carve after they were tightened no less than 20 minutes earlier. I carve into MDF mostly for signs.
sounds like losing steps… check:
-tightness of belts
-loose v wheels (i recommend reversing the screws and nuts on them so they dont come loose, look through the link at the bottom which highlights it)
-calibrate your steppers
I have links to all of these (not updated, so I’m sure theres more info out but these are a good start)
Don’t scrap it send it to me 
just kidding. What screws are becoming loose? I would say check the forums on missed steps. 2 inches is more then way off and sounds like you might need to make an adjustment to the pots to get the correct voltage to those steppers. Don’t know what controller you have but that would be something to look at.