I've had problems with my S15 gen 2 Connect that have gotten progressively worse.  In addition to this device, I've got 6 Play:Ones, one ethernet connected for Sonosnet, that are still running normally.   I'm running S2. First, the S15 showed up in my system and played for awhile and then would stop playing.   Tricked it back in by joining a group but went away fairly quickly.  Then it disappeared from the system altogether so I did a factory reset and added it back into my system successfully but it went back to playing only briefly before stopping.  

Now it has vanished from the system again and won't progress to the flashing green point of a factory reset.  Flashes white 4 times fairly strongly with slight flickering on the 4th flash and then stutters on the 5th and very faintly has orange on the pause/play button.  Continues to cycle through like this.

Okay.  Plugged the Connect into the router directly.  Now will flash green for awhile but then not.  Successfully added the Connect back into the system during one of these green intervals.  Now status light alternates between normal steady white and flashing white but almost entirely flashing.  Plays when steady, disconnects when flashing.  

So, back to where I started, really.  S15 is in my system but will only stay connected briefly.  

I'm leaning towards the S15 being in the process of dying in some way as I'm having no issues with the rest of the system.  Regrettable, since the S15 was running nicely in the S2 app until now.