Flashforge Creator Pro 8mm-bolt holder for spool holder

There are many spool holders for the Flashforge Creator Pro. Some use a bolt or rod. I'm not reprinting the existing parts for holding the spool on the rod, only the part to hold an 8mm bolt (I use 120mm in length).
This was created in sketchup and carefully checked for any hidden artifacts inside or for flipped surfaces, and then converted to stl.
The stl file will print fine with Flashprint.
The stl file will result in bogus code and sometimes crashes with Simplify3D. If anyone has an idea