So, I have been using these headphones, connected to my laptop for a year - and very happy.

Recently, I installed the Sony Headphone app on my phone - I don't know why is that related but maybe that app pushed a software update to the headphones which destroyed them?

Now, the headphones initially work as usual but after a few minutes they play a chime "too doo doo" (ascending tones) and stop playing the sound from my laptop.

After a few minutes, they play a similar chime but the tones are descending and I get "reconnected" to my laptop.

I want to emphasise that the Bluetooth on my phone is ALWAYS OFF, expect for a short period where I was listening from my phone - but I am not listening on my phone anymore!

So, what is this chime from the headphones trying to tell me?
How to stop the headphones from disconnecting?