Heart rate sensor disconnect connects repeatedly

My Edge 540 with updated firmware 20.19 has a problem with connection to the heart rate sensor sended from the Venu 2S.

This was working well till some weeks ago, but suddenly stopped working.

On the Edge I see repeatedly connect / disconnection messages.

I tried to to remove the connection and re-add it, and I tried the same thing from a Venu 2S plus. But same problem.

I also have reset the Edge. But that did not solve this.

Anyone knows how tolsolve this?