3D Print file prep for wheel rims - STL producing "holes"

I’m working on a design where I need to produce a printable file from Blender 2.8. Looks fine when I export it as STL and reimport to check. But as soon as I bring it into a slicer sofeware like Matter Control. I’m seeing holes in the design around specific areas. I don’t understand why. Can someone help?

I included images of what’s happening.

did you convert everything to mesh before exporting or are you using subdivision surfaces ??

try doing a remesh with a modifier or quadriflow remesh

That’s a good point. I haven’t tried that yet. I’ve done a bunch of other stuff to repair the mesh, but i hadn’t seen an article yet that talked about it. I did, however, discover that by scaling up the model, the issues are alot less pronounced. Not sure why, but maybe that’s something.

Thank you man. Really appreciate it

Weirdly enough, scaling up the model by a factor of 100 and then exporting it to STL worked the best. Since the client is using Matter Control to slice the file (which was creating the holes), up scaling helped fix the issue.

Thank you for your reply!