Apple watch 7 microphone stops working frequently

I have a weird issue with my Apple Watch 7 (stainless steel, 4G model). Sometimes the microphone does not work and seems to be in use by something else. For example; I receive a call, answer on my watch and the person calling me does not hear me. Rarely it does work though..

Same is valid for operating Siri, or recording voice memo's, or when I open the Sound app it tells me the microphone is in use and therefore measurements cannot take place. Also the voice memo app does not record anything when I have the microphone issue.

I performed a reset, microphone is not blocked, no case or anything is used. No joy....

I have contacted Apple for this issue and they have checked the watch using their diagnostics tool and nothing was found.

The Apple support representative told me that it might be some software issue, but searching for this issue icw a watch 7 didn't gave me any direction that this is indeed a software problem.

Does anyone has a clue what this could be or which actions I could perform to resolve?

This drives me nuts because I can't use the Watch the way I would like to....