Hi Paul, so it looks like the main thing with a real degeneracy problem is a little thin sliver along the back. On the back side I noticed this anomaly here:



Then deleting the large back pieces I could get a little better look at it:



Often times that kind of shaded triangle "leak" can be because of degenerate trim boundaries. I zoomed in closely to that area and there are some very skinny slivery faces in there, these seem to be likely culprits:



So maybe something like the curves along the back side didn't quite exactly align with each other and are leaving that messy little fragmentary result in it.

Or maybe there is a tiny line segment in one of the curves. Something akin to that probably. If you can maybe post a simplified file that has just the curves used to create that piece that would help me to examine it more closely.

But it's likely that spot with such tiny compressed/degenerate surfaces in it are causing boolean problems.

- Michael