On deployments with multiple gateways, opting for automatic firewall rule creation via "Register rule" or "Pass" creates rules that do not include the advanced mode "Reply-to:" configured, so if a query comes via GW1 it will probably return via GW0 and be dropped.
Solution is to set to manual and enter your desired reply-to gateway in the dropdown.
Hope this helps
Can you raise a ticket on GitHub about this? This may require a bit of discussion.
Thanks,
Franco