Martin417 - Good luck with this... it only gets worse. It starts with that, then other sync settings will be lost and it starts switching back and forth between default settings and your settings randomly. Like Bluewaterbum said, phones stop connecting and require you to forget and then setup all over again every time the vehicle is started. Eventually, the screen will just blank and you can't do anything except change the volume.
There are forums all over the place talking about this issue and Ford stating its an APIM issue. People have paid $1200+ in parts and labor to replace the unit, only for the issue to come back.
I called Ford Sync support and they are aware of an issue but have no ETA on a patch or update and just told me to go to the dealer with my case number, but they won't be able to do anything.
IMO - Best thing to do until they release a new update to fix this is to master reset the head unit. This will buy you a month or so per reset. Don't waste your time with Ford support or the dealer, they just take your time and money.