Relief Challenges

So I’m a Zelda geek and had to carve the Master Shield. I found a model online for Fusion360 and did some minor modifications to it to make it flat on the back. I exported to STL and used CamLab following the basic instructions from Chris’s landscape relief carve. What happened was every once in a while on the edge of the shield it seemed not to follow the contour and actually cut into the side and past the bottom.

The model looks fine in both Fusion and CAMLab, but both times I’ve carved this I had this issue.

Might be hard to see, but you can see the carve video where it punches into the wasteboard a few times.

Any idea why it randomly goes past the model bottom?

I can post the various files if needed.