Thanks mate. I totally can't explain it (because I'm not sure what I'm doing)... but running STL check made the bad polys disappear... *fingers crossed* ;-)
Yeah that model's a mess. Some older models tend to import incorrectly too. I had an experience like that while trying to import Google warehouse models. Best of luck to you. I don't think STL Check can clean up a model like that. It just checks for mesh errors.
Thanks BlastradiusO I didn't, but the modeler may have. In the whole model, there are about 20 polygons that seem to be 'off' in the same way. There isn't a turbosmooth modifier in the stack, but of course the modeler may have collapsed it. This helicopter is from Evermotion's Archmodels collection (number 84 - military…