I have both Bose Soundsport in-ear headphones and also QC35 headphones - both bluetooth and both able to connect to two devices at once.
I have 3, sometimes more devices I use with these and I have to often re-pair when I'm swapping over. Typically I use an iPhone x, an iPad and a Macbook Pro - if it's useful to know.
If I'm making business phone calls I often connect either of these headphones to my iPhone and sit at my computer to take notes during the converstions.
I often notice a corrupted 'bubble' or a quiver in the quality of the audio which makes me sometimes not hear the caller very well as if they're breaking up. They don't seem to have a difficulty in hearing me at all. This has gone on for many months and I can probably demonstrate this phenomena in a test environment since it behaves quite predicatbly on pretty much all calls I make.
I have recently noticed that if my laptop is connected via bluetooth as well, I can disconnect it from the headphones during the call and the quality with the iphone improves with the corruptions stopping. My laptop isn't muted during these calls, but neither is it making any sounds. Wondering if this is a good practice to follow or whether, since the Bose devices are designed nowadays to connect to two devices at once, whether I should look further into the cause of this issue. I'm pretty sure I've experienced this with the iPad and iPhone together too.... I don't seem to experience issues like this with listening to music through any device.
It's frustrating to me at times since Bluetooth still isn't an exact science and I quite often have issues as I tether and untether devices and it's tricky if I have to mess about with these setting during a call when I'm trying to make notes and chat at the same time.