I had the same Problem and i went through it with the support , escalated it to the second and third level, nobody could help.
BUT! i found a solution, its not a nice one but for me it did fix it.
Just stop using Spotify over Carplay and use Apple Music instead.
I tried months to fix it otherwhise but only after deleting Spotify from my Iphone the bug was gone.
So this is crazy but unfortunatly the only way that i could fix this issue. I hope that this will be solved from apple soon, as Spotify was easier and nicer to use with the family option as it is with apple music.
hope this helps!
Works for me since 3 months now, never had a problem again
Iphone 11 Pro (latest update)
Watch 6 (latest update)
BMW X5 (F15, 2019) wireless Carplay