Weird clipping problem when importing an obj in another program

#1

I couldn’t upload more than one image so here are the images: Link

I’m trying to make a pretty regular shape and when I import the obj into Paint 3d or simplify3d I get this weird clipping problem where it ignores one of the corners and just draws the line across (left window in the first image)

Also, on this little piece, it’s putting a rectangular top over the circular gap when there isn’t one
(next 2 images)

#2

From what I can see, concave polygons are rendered rather convex.
What file format did you export? Did you check in the export options to triangulate faces?

#3

That fixed it. Thank you!