In my experiance, whenever i connect another cable behind some Home Theater component, especially the AVR, i inveriably upset the HT gods and end up with a couple of dodgy problems to resolve.
Seems those HT gods just try to make my life hell becasuse i use cheap cables and connectors
In my case, my RPi running LibreElec (kodi 17 i think) is cabled to AVR using a HDMI cable while the AVR uses another HDMI cable to conect to the TV.
Due to a curious cat, or those HT gods, i'm always fiddling with the HDMI cable since the Pioneer AVR has crap quality HDMI female connectors resulting in lost picture or lost sound.
Yeah, the digital theory is that you always have sound AND audio, or nothing, but i guess it's those HT gods just messin' with me.
Sometimes that cat or those HT gods keep messin' with my audio as i also get cracks and pops or a speaker goes quiet.
So, it's just a quick look at the back, expecially around the speaker wire teminals, and i'm again hearing quality sound.
One day i'll tidy it all up and make a sliding shelf with a cable management arm for each component using quality connectors/cables so those HT gods will be happy and stop hassling me
And that curious cat will have less an impact
As to your problem, maybe some prays to the HT gods wouldn't go astray but for more worldly help, it would be worth specifying how you have cabled up your Kodi box to the AVR and to the TV (that is, the type of cable used, where they go, etc). Then someone may be able to help with specific deatils and things to check
