grouping is not the problem. paired speakers are. your experience
suggests its actually a combination of a "paired speaker" inside a
"group". Sounds like you can unpair your paired speakers and then your
speaker groups will function without problem.
I unpaired the only "paired speakers" I have in my house, and I haven't
had ads since (5 days ago). I still use speaker groups and there is no
issue with speaker groups for me. If you are unclear on the difference
between "speaker groups" and "paired...