Mine did that a few times on old software. Since I updated to the latest available I haven’t had any freezing.
When it freezes you can do the following to restart/reboot the system.
SYNC 3 System Reset
The system has a System Reset feature that can be performed if the function of a SYNC 3 feature is lost. This reset is intended to restore functionality and will not erase any information previously stored in the system (such as paired devices, phonebook, call history, text messages, or user settings). To perform a System Reset,
press and hold the Seek Up (>>|) button while pressing and holding the Radio Power button. After approximately 5 seconds the screen will go black. Allow 1-2 minutes for the system reset to complete. You may then resume using the SYNC 3 system.
Here is a post to all of the latest versions.
https://www.expeditionforum.com/threads/comprehensive-posting-of-sync-packages.40051/