Take a look at this info,
This is version D207. This update came out around the end of October. Previously the newest version was D25.
(This is what I upgraded from, let me know what yours is at. Yours being a 2015)
1. improved stability , fewer reboots and blank screens.
2. reduced XM loading message
3. resolves intermittent audio issues
4. corrects sound levels not corresponding to settings for bass,treble etc.
5. adds the ability to reboot the unit by holding the power button on the audio unit.
6. Adds S/XM Smart Favorite: allows pause/rewind and replay features like on a DVD player.
The TSB is NTB 14-079 (i think this might be the same TSB number as last time, not sure.)
The USB music still has a lagging effect

on mine.
Let us know, Thanks