I have 17K miles on a 21 ST and have had this issue for about 4 months now. Suggesting that I take more frequent trips and that the trips should be longer than a short ride. I took it to my local dealer and they said that they couldn't get it to "throw a code", therefore they had nothing to troubleshoot. I took it to O'Reilly's to get them to check the battery/alternator. They said that there was something drawing the battery down.
I have NO confidence in a $55K vehicle that tells me that I can't leave it in my garage for 4 days without losing battery power.
I contacted Ford Customer Service. What a joke. I traveled the world in an hour. Philippines, Columbia, Houston, Michigan. Started a case # and was disconnected and was not called back. They ASSURED ME that there was nothing wrong with the battery or charging system, but that it is a FordPass issue, or a Sync3 issue. I've updated BOTH, and the problem continues. I'm actually considering GETTING RID OF THE VEHICLE because of my lack of confidence in it and Ford "quality".