Sync Scheduled Maintenance?

[BooYahDad]

Today, I pulled into a parking spot and turned off the car. After I got out, I locked the door and looked and saw the Sync logo on the screen. It said something like "performing scheduled maintenance" and had a progress bar.

I couldn't stay to see what it was doing, but any idea? I had never seen this before?

 

[cnsheets]

System detected an error or malfunctioned and rebooted. This is typical with the current MFT.