Both devices are upgraded to latest versions:Probably some driver needs an update in RouterOS.
What RouterOS version are we talking about?
You mean like this:Or add you public IP as dst address in your firewall rule. you may have to remove In Interface List as well.
Thanks!Easiest thing is to setup dynamic routing between them and then FW rules to permit the traffic.
For instance:
HQ: 10.0.0.0/24
B1: 10.0.1.0/24
B2: 10.0.2.0/24
B3: 10.0.3.0/24
FW rules accepting 10.0.0.0/22 to 10.0.0.0/22