{{active_denon_{{clientname}}}} will track as it is tied to the SelectDevice command.
Since I cannot remote into your server can you email me the html page(s) that are in play?
Thanks Dave but I have already solved this 2 nights ago. It took the nuclear option of removing both receivers and re-doing their setups but I haven't had an issue since then.
If this ever crops up again I'll get in touch with you immediately so you can take a look. Thanks again!