Can't access internal network from Wireguard client

[KonKom]

Hello all,

I'm a bit lost with the configuration of my Opnsense. I don't even know where to start.

I have 3 physical ports on my opnsense router, connected to Network A, B and C.
A and B are bridged, sharing a subnet, and with routers behind each port. C is with its own subnet.

Wireguard is working, the client can access subnet C and the opnsense itself. I can't access any IPs in A and B though, and I don't understand why.
The Firewall liveview shows the traffic as allowed.
Traceroute under Interfaces: Diagnostics: Trace Route and with the Wireguard client as source gives me a "traceroute: bind: Can't assign requested address" and traceroute from the client itself says just failure.

Is the bridging the problem?
What else can I do to find out the issue here?

Sorry for not posting any configuration, but I dont know which one.

Thanks for any advice!