IPv6 bridge address might go unused
Configure a client with the IPv4 and the IPv6 address of a bridge. One of them are going to be "preferred", as pointed out in logs (notice level). It happens to be the first Bridge line that becomes preferred. Regardless of which is preferred, two connections will be established with the bridge, one over IPv4 and one over IP6. When the IPv6 address of a bridge is reported to be preferred, the IPv4 address will still be used, it seems.
This is because we already have a connection, the IPv4 one, so there's no attempt of setting up a second to the same bridge.
This bug should be fixed as part of the work with making the connection code aware of the multitude of addresses, probably by replacing the node->is_running flag with a flag per node address.
The workaround for clients that don't want to use the IPv4 address of a given bridge is to remove it from the configuration.