make sure nothing is marked to export or import for runtime sharing.
Thanks that gave me something to investigate but alas no, I checked all the symbols properties and nothing is checked for runtime sharing.
Any other thoughts?
I might try renaming all symbols when I duplicate a document but that seems a lot of work.
If you don't have anything marked as runtime sharing that is the only thing that would modify the symbols. Once you duplicate a .fla file it does not have a magical connection to the others. I would just audit your process and make sure you are modifying what you actually intend to modify.
Are you modifying any external assets outside of the FLA that maybe they are all still pointing to?
there's no other way a change in one fla would affect a different fla.
do some tests to confirm.