My Beats Studio Buds + microphone disconnect / goes on mute during calls

My Beats Studio Buds + microphone disconnect (means goes on mute) suddenly during calls either on the iPhone or my Mac; can be ordinary calls, or what's app calls, or zoom / teams meetings, without me getting any noise signal (no bip) or any other notification. I just understand it by people on the other end asking whether I am still there or asking me to unmute. I have disconnected, disregarded, and reconnected 2-3 times the device, but it does not really help... And I have not dropped them or the case, or squeezed or made them wet.

Otherwise sound quality and call quality seems rather good, when it works...

Please advise!!!

Many thanks

/A