It looks like neither of these will work because the persistent connection is established by the Parent relay.
And the client on the child relay connects to itself as localhost (is this correct?).
I need relay to relay persistence from child to parent.
I’ve added _BESRelay_GatherMirror_UpstreamCheckPeriodMinutes but it doesn’t seem to have made a difference.
I don’t really understand why this would work, but I guess this is something I can try by setting up a DNAT to the child relay.
Child Relay notification with NAT