Hi Keith, so the problem seems to be some messed up edges in this scalloped out area here:





I separated out the surfaces for that area, then untrimmed and retrimmed them, and then rejoined them to get it fixed up, it looks like the fillets there end just very slightly off alignment from the closed surface seam for the scalloped surface and that was confusing the joining process, I had to join things back in a particular order to get that spot to work ok.

Please try the attached 3DM file and see if that works better for you now. And if you can send me the crash dump report for the crash I might be able to see what's going on with that too.

- Michael

Thanks for your suggestions Martin and Kevin, I did try both and although neither worked this time they were new things for me to learn. Michael fixed things overnight. Great customer support, thanks Michael.

While casting about for solutions yesterday I noticed that Moi is not on the Blender Wiki list of computer modelling programes. Seems a bit of an oversight.
Best wishes
Keith