Bumping this older thread. My Slacker favorites have been disappearing for a while now. Not sure exactly when but I got my 2014 P85 in May '16 and the problem has been around in some form since I started really using the Slacker capability a few months later.
Lately, the problem is only getting worse. My 2 top stations lose their "favorite star" within a couple of days or less, now. I've even had this happen literally as I put my finger on a station - it just disappeared! The only workaround is to scroll left to Recents and re-select the star again as Favorite. I've had some lesser used stations just disappear after not realizing for a few weeks that they had gone lost Favorite status.
Another recent oddity is some stations going "gray" - the icon just changes to solid gray, and the station no longer works at all but still shows up.
This is really aggravating. I have a USB drive with a ton of music but the interface is not what it should be so I've been using Slacker more in the past year. But Slacker has turned into a bugfest too. This is really disappointing.
Edit: A few things that I've done. None of these seem to have made any noticeable impact.
* Got a Premium account for a year and used that. No discernible difference in this respect.
* Logged in/out to my account or car account. Logged in to both on web browser to try to customize stations. (Could do more on my account than the car account.)
* Rebooted the MCU many times.