Bug: Bose Headset looses Audio on 2nd call microphone is still active

After many calls where I had to switch my headset off-and-on-again I took 15 Minutes to reset the headset, unpair all bluetooth devices and still no difference.

Than I took my other phone and called myself to find to my surprise that it was the same behaviour with phone calls. After some more investigation I found the root cause: The headphones were just completely turned down  I don't know how that can happen since I'm listening to music at a certain level, I'm having a phone call with the headphones and it's fine and at the next phone call there is no audio whatsoever. I'm not sure yet if it is an issue with the iphone in conjunction with teams or if it is an issue of the headphones. Since I didn't change anything about the headphones I'm still suspecting teams (and since there are quite a couple of other bugs...)