Doorbell video not available after ringing “cam not available, wait until nobody is streaming..”

Every time (almost, see below) someone rings my Robin ProLine HomeKit doorbell, when I tap on the notification on my iPhone, the stream is not available. It claims someone else is streaming which I know not to be the case. The doorbell has become useless. It improves for a short time after a restart (power cycle) of the doorbell, but that’s no way forward.

Background: there are 3 “persons” in that home, two have an Apple Watch in their account. There are 2 HomePods gen1 and a HomePod mini, as well as 2 AppleTV 4K acting as hubs. I am recording to iCloud and have selected a zone to trigger saving.

Any help would be most appreciated! Thank you!