Dynamic DNS problems on Synnology with Orbi RBR50V2 firmware 2.7.3.22

Mention of the Orbi starts about page 3 of the thread.  I get the impression that this might be another consequence of the V2.7.3.22 firmware.  This thread provided an interesting perspective on DDNS. (which I enjoyed.)  It had never occured to me that there could be any number of DDNS entries that resolve to the same public IP address.  As long as the connection request refers to a port that has been forwarded to a specific IP on the LAN, any number of devices could be using DDNS. They just all have to have different ports on the Orbi WAN side.

I also noticed a comment that the Orbi debug page (at one time) had an option to prevent automatic firmware updates.  I do not recall seeing any such option, at least in the past couple of years.  A mystery.