Hello, I am facing the same issue, but this is the first time I have enabled "host access to custom networks", so I cannot say it's related to the Unraid version. My br0 custom network type is macvlan.
Unraid IP address 192.168.8.8, the container using br0 has 192.168.8.107. I can access the container from devices outside Unraid, while I cannot from Unraid itself and other containers not on br0.
I have temporary fixed creating an LXC container, and running the container there.