Hi @Kyle Brown
I went back through my save files and turns out i have a save file at pretty much the moment the game changes from a career save to a network save.
I've uploaded the save file and it is called career_to_network_on_job_offer_negotiation.fm
I have a job offer from MK Dons, if I decline the job offer it appears the game stays as a career save, but negotiating the job offer (even if talks breakdown) sees the game turn into a network save with "Relinquish Control on Client" appearing on the "My Profile" menu.
EDIT - I noticed that in game preferences under "Online Game Preference" that "Allow users to join your game" was set to ANYONE, I changed this to NO and it seems to have stopped my save from changing to a network save regardless of whether I negotiate, accept or decline the job offer.