Webcam Permission Issue with Firefox and DroidCam

I’m using Win 10 and Firefox 96.0.1 (64-Bit) combined with latest DroidCam to use my phone as a webcam and share over watch2gether.

Everything worked fine until i switched DroidCam to 16:9 (1080p).

That resulted in following bug:

as i tried to enable webcam i got the following message:
“Das Gerät konnte nicht aktiviert werden. Bitte überprüfe die Berechtigungen, indem du auf das Schloßsymbol neben der Adressleiste clicks.”
(bascially it asks me to check permissions)
Permissions are fine so i tried clearing cache, reinstalling droidcam and firefox, nothing helped. I can use DroidCam HD Mode with Chrome, Discord, Windows Camera App, etc…

the problem only occurs when switching to Full HD and accessing watch2gether using Firefox (chrome is fine)

any idea what could be the problem?