Community
I have a quick question.
What version of STEP?
Can you Attach an assembly and resulting *.spt file here that exhibits this issue?
(Is the issue reproducible? Can they make up a simple dummy assembly that exhibits the same issue?)
Can you open the exported file with the version of inventor you exported it from?
If not, is an export issue.
If it's fine, try saving it as an older step version.
Exploded parts could be due to you having multiple files with the same name, just in different folders. Step files can't deal with this and use the first file they come across.
Can't find what you're looking for? Ask the community or share your knowledge.