Hi, can you verify with TORCH on both interfaces to see what ports and IP addresses/MAC adresses are passed, and which are missing.
Traffic to or from the bridge itself (to the router itself) will never pass to the other interface. (Winbox, terminal, snmp, syslog, DHCP, DNS ... and other services)
The bridge has many options about broadcast and multicast forwarding and the possibility for limiting them.
STP handling by the bridge, BPDU packets, and other bridge management traffic is not forwarded.
Some MAC addresses are not forwarded over a IEEE compliant bridge (reserved MAC addresses)