I got my v6.1 working a couple of months ago and everything works perfectly except an audible high pitch buzzing can be heard from left channel trough music and very clearly for a few seconds after music is paused.
All joints on the board look clean but still went over them with soldering iron without improvement.
Any help would be appreciated about what to look into next.
this seems to be more of a common promblem. I have never experienced it myself, but it occured on modules I build for other people. One of the modules has been installed by a workshop and they reported something similar to your issue after testing it. Interestingly this issue did not occur during my testing after I finished building it and the owner of the car could not notice any distortion either.
My best guess is, that it might me a problem with the audio codec, so maybe try another device.
As far as I know, this distortion only appreared with samsung phones.
I have not received any further reports yet, but i will come back here as soon as i know more.