Xbox app updated the game automatically, disabled auto updates now, but the damage is done apparently. No downgrade functionality in the Xbox app as far as I know.
“Due to a recent update, the save file is no longer available”
Not sure if it’s related, but the “continue” function on campaigns is also broken now. Always restarts some old map/year that’s already completed. Does not resume the latest save (or restart last map) as you would expect.