unpredictable mesh generation

[Jake]

After examining the scene the problem seems to being caused by the spline's RestrictTo2D mode in combination with Dynamic Orientation. If you disable 2D, you'll notice the orientation rolls in curves (like a plane would fly the path), but using 2D makes the dynamic orientation pointless.

I switched Orientation to Static and set a proper rotation (-90,0,0), then it looks like expected.