The same thing is happening to mine yet the sync doesnt give a % meter. Just endlessy syncing and when i exit the screen, a quick 0% shows up before crashing the game regardless of how long i let it sync. Ugh. Im so done waiting for this fix.
You need to wait until it finishes. The files are ridiculously large for an Xbox game save. Typical games have save files 4 - 10 Mb whereas Forza files are well over 100 MB. The console wasn’t made to deal with that so it takes a while - just be patient and let it sync. If you don’t you will lose your game save and there won’t be much sympathy for you here.
Search for previous threads containing conversations regarding this for all the reading you may or may not want to do.
Thing is I never quit the sync which i stated above, it just stopped about half way and since it stopped by itself, my friends went on different games so i didn’t try again until a few days later which is when i found out I was reset.