Wireguard does not rout all traffic over the tunnel even with 0.0.0.0/0

I have a raspberry pi with a Wireguard Server and a number of peer's Android, Windows and another Raspberry pi. The tunnel works on all clients (for example i can ping my upnp server). The thing that does not work is that on the Raspi client it does not find the upnp server. I can ping the server but kodi for example can not find it. On the other clients it does work. VLC for example can find the server on these client's but only when i set the allowed addresses to 0.0.0.0/0. I guess that this some routing thing or the way that a upnp server works.? So i did the same thing on the pi but still it can not find the server. But ping is still working. I was wondering if this could be because i connect the pi via wifi? Maybe someone has an idea. Thank you for your help.