Puzzle Generator app and Accuracy of Cut

So I tried out the Puzzle Generator app today, and the generated shapes/pieces seem correct. When I cut them out though, they don’t go together well. The curves don’t quite match, and the knobs don’t quite fit the notches. I’m not sure if there is some calibration that’s off for my machine or what else could possibly be causing this issue.

My initial cut was with a 1/8th bit in 1/4 inch plywood, and the pieces wouldn’t even go together. So then I tried a 1/32nd bit in 1/8th plywood and got the lower four pieces in the picture. You can see where some spots are really tight, but there are also gaps in other places. Even around the same knob/notch pair it will be tight on two sides but have a gap on the other… The upper four pieces I cut “on path” instead of “outside path” to see if that would give me a little wiggle room so the pieces would fit better (in theory should have just been 1/64th smaller all around, right?), and it did give me wiggle room, but far too much! And the shapes still weren’t a good match.

I’m really not sure what to try next. Is there a sample cut I can do to see if my machine isn’t calibrated quite right? I’ve had this X-Carve for 3 or 4 years now, but apparently haven’t done anything that needed this specific precision. Any thoughts?

I suspect “play” in your machine is the main culprit (assuming its calibrated)
Any play or backlash component will make your bit trail a little behind true path, and will be especially apparent when transitioning between X/Y direction.

You can test this by carving a true circle with 1/2" or 1" diameter.
If your machine is not firm enough you’ll notice that the smaller cirle will appear loopsided.

If that’s the case would the solution be tightening belts? The cut takes a handful of passes, what are the odds that those passes would all end up having the same variance?