Cuts offset on the X axis

What happened here?

I am using MeshCam to create the toolpath file, and its never done this to me before. Maybe there is something loose on the machine? I checked the belt and the V wheels, and they seem fine.

CORRECTION: I just checked one of the screws holding down one end of the belt, and it was loose. Just to be sure, would this be the cause of the problem? I am going to try to cut this again in the morning.

Most likely, yes.