Just adding my problem to the list here.
I'm an audio producer so always hesitant to update to a new OS. finally updated to Monterey 12.6.
Playback through my aggregate device is completely distorted when I play anything from Spotify or through a web browser (youtube, etc)
I don't experience the problem when working in Logic Pro, or when playing audio files saved locally.
My temporary workaround has been to change the system sound settings output to a single audio device, rather than the aggregate, to listen to Spotify. This is less distorted, but actually still sounds pretty terrible, I think it's in mono actually.
I'm at a loss, not sure if I should roll back to my previous time machine backup or... deal with it?
In any case, I can't believe there hasn't been an update to address this issue - it's a BIG ONE!
iMac (Retina 4K, 21.5-inch, 2017)
3.4 GHz Quad-Core Intel Core i5
Aggregate Audio Device: Universal Audio Apollo x8, Focusrite Scarlett 18i20