Awful high pitched whistle in headphones with audio tones

Got my Fenix 6s Sapphire in April and use the Backbeat fit wireless headphones.  All worked perfectly for a few months.   Suddenly all km audio prompts were announced with an awful whistle sound.  Button press, phone notifications were similar but not so loud.  Put up with this for a week assuming it was a headphone problem and then on a run the headphones just stopped working completely.

Replaced my headphones and upgraded to Backbeat 3150 and from the first use I had the same problem.  Now the headphones have a slight crackle on certain tracks.  I have logged a call with Garmin support, the forums were down at the time so I couldn't search for other users with the same issue.  I was asked to provide a video of the issue which I did but a few weeks have gone by and I can't get any response from Garmin.  I did find a thread on reddit that said known issue and to turn off audio tones which has helped but I am still left wondering if the sound on my new headphones has been impacted and if it killed the last pair. 

Has anyone else experienced this?

Click here to play this videoClick here to play this video