[Jeremy]

Hi there,

Can you share the file?
I'm curious to see exactly what happens.

Generally the imported part shouldn't slit itself in different files, this is the point I want to investigate.
One thing that you could do in this situation is to import your part in a reference frame and rotate that reference frame.

If the STL file is IP sensitive, let me know, I'll give you my email address.
Have a great day.
Jeremy