Unable to make a call with more than 2 Member behind the same router

Good morning,
I’d setup a nexcloud 18.0.6 with talk.
The turn and coturn server are working too.

The problem is, that only 2 member behind the same router, can simultaneously make a call.
If the 3 member connects he will get a black screen. After disconnecting one of the first members the 3 member will work fine.

Is there a restriction in talk or do i have a misconfiguration?

I think you know the configuration in [1]. Perhaps your server is wrong located or not accessible. I can not solve your problem. But perhaps you can draw a picture with your actual structure. Perhaps you also can upgrade to Nextcloud 19 and the better talk app.

[1] https://nextcloud-talk.readthedocs.io/en/latest/TURN/

Thanks for your reply… This is the construction.

Ok i think it is ok. Can you test three devices behind your router and additional behind another router to include or exclude your router from the error situation? But normally it should work with NAT and every router.

Sure… I will test it and give you a feedback