I have created assembly in which I have numerous models and say when I created 2,3,4 and 5.  I created model #2 and did a save as "2R" than I created a mirrored part called "2L" than I created assembly's of "2R" and "2L" which include assembly weld features. I also did the same thing for #3, (I don't think it matters but 2L & 3L sub-assembly's make the Left hand assembly for part #5L.) So well in the process of working on the assembly of #5L and I save and close the assembly file it always wants to rebuild and the assembly for #5L and also is looking to save changes to the model for part #2L is open.

Why is it that only one model is opening up in the background? The model is only one part of a sub-assembly that was inserted in another assembly.

Any clue on what I might have done or clicked to create this in the sub assembly? was it during insertion or somewhere in the creation of that assembly?

Yes, I am relatively new! We jsut purchased SW and recently complete essentials, so take it easy on the newbie