My man, thank you so much for the quick reply and targeted thought. I think this is exactly the same advice I read before with someone else but, as I mentioned, couldn't find the thread. Do you think when restoring the head unit, cables are crossed and causing that (and if so, which ones would that be)? Is this something grounding tape/copper foil tape could be use to insulate the power cables or AUX cables and it remedy it? Thank you.

Edit: Do you think something like this could do the trick? https://www.amazon.com/Mpow-Ground-Isolator-Stereo-System/dp/B019393MV2/ref=sr_1_3?dchild=1&keywords=ground+loop+isolator&qid=1595958072&sr=8-3

The Micca Origen MIGHT solve your issue but if your power hum extends to your USB it will pass over. I ended up using a Ground Loop Isolator to fix my issues but that can mess with the frequency response.

Ground loop isolator

https://www.amazon.com/Mpow-Ground-Isolator-Stereo-System/dp/B019393MV2

just a cheap one off amazon. LINK