Same with me. In my multiroom setup there are 2 JBL Playlist devices and several other chromecast players. In a first step by the end of last year, all groups that list both jbl playlists, only one of them played. What was really annoying: they played alternating in a random sequence. The groups that listed only one jbl playlist (and several other devices) still worked in these days. Therefore I changed my setup and my groups.
In a second step (for a few days or weeks now) the jbl playlist devices do not work in mixed groups at all. Not even in mixed groups containing just one playlist.
I guess, the problems are caused by the old chromecast firmware in playlist devices (1.28). The nest devices use (e.g.) 1.54 nowadays. And google changed a lot especially with respect to groups (since google lost a trial and had to remove some features due to violation of some Sonos’ patents).
However, if I am right, the only chance to get this working again is that jbl updates the chromecast firmware. I asked them if they are going to prepare updates. But no answer so far.
