Uniti Atom HDMI ARC Testing Weirdness

Hi Everyone,

I'm not up to speed with HDMI ARC and audio format constraints if any.  I have something weird going on and wondered if someone has the knowledge..

I'm just hooking up HDMI ARC for the first time for testing.  I wanted to ensure the ARC card was working ok after purchase. I'll use it in the future one day when we downsize, but it won't be used for a while.

My test 'lab' is a Uniti Atom, hooked via HDMI ARC to a Panasonic TCP50GT50 Smart Plasma TV.  IT has an HDMI ARC port and uses 'Viera Link' nomenclature for setup of that port. The TV is networked and sees a number of DLNA servers ( Music, Movies on a QNAP, the NAIM), a HDHomeRun DLNA OTA tuner, and it also has a Netflix app.  Everything works fine through the TV speakers.

Here's what I've found:

DLNA Music - everything works ( on/off,volume, HDMI input focus ), music comes through

DLNA Movies - everything works, sound comes through, controls work as above

HDHomeRun - I can hear sound in DLNA preview (DLNA browser on the TV), but when I 'select' the channel, the sound changes to a mid-frequency 'bad ignition coil' sound. Control functions work ( on/off, volume, hdmi focus)

Netflix - Control functions work, only get the ignition noise sound.

I read over on the HDMI website, that HDMI cable shouldn't matter.  I've tried two, made no difference.  I've looked to see if there are ARC audio settings to change outgoing encoding or something on the TV, but no it doesn't. Also looked for audio channel control on the HDHomeRun and can't see it there either.

Anyone have any ideas?  I figure it's an encoding issue, but can I get the details? Much appreciated