When saving an assembly that is built without parts that include multiple bodies, STP works well. However, if your assembly included parts that do have multiple bodies that are suppressed for the purpose of the assembly, you will see this question during the save process:
But this must be a rhetorical question because - for me at least - has absolutely no affect on the output file. I select "No" and then save. When I, or anyone else, opens the STP format, all the hidden/suppressed bodies are still there. Makes for an unrecognizable mess.
Any suggestions on how to get this to work as advertised?