Needle Cutter with MPCNC, Second Pass Not Cutting on Same Line

Hi all. The last two days I have noticed that when I am cutting out rc plane plans with my MPCNC, on smaller rectangular cuts the second pass doesn’t cut on the exact same line on one side. I have my cut through lines cut with two passes, but what is happening is that on the second pass one side of the rectangle the cut does’t cut over the the last line as the other 3 sides do. Is this a setting that might be off in Estalcam? Or perhaps loose belts? It doesn’t always happen, and only on small rectangular cuts.

Step one, check the pulleys.