I have set up a group of two Google Home units and I am using the Cast option to play music to multiple rooms from my IOS app.
If I cast to one Google Home only everything works as expected, I start the playlist and it works fine.
When I cast to the group after every song the playlist stops and it is like it was never started. If I check on the IOS device I started the cast from, the queue is gone and I need to restart playing.
When I cast to the group from my Android tablet via Plex it works fine, just on my IOS devices.