When playing video on Kodi, input switches back from Pi to TV

I am running a Rasp Pi 3 with LibreELEC and Kodi to my TV through an A/V receiver (so I can run the sound out of the speakers or put it on pass-thru mode and run it to the normal TV speakers). The TV (older Panasonic plasma) and the receiver (very old Onkyo) are CEC-enabled. I switch the TV to the HDMI input to use the Pi, but then when I start a video in Kodi, the input abruptly switches back to the TV.

My theory is that there's a moment when nothing is being sent from the Pi to the TV, so the TV or receiver up and decides to switch its input back to the tuner. Wondering if anyone can help because this is a rotten glitch to deal with.

Quote from smp

Maybe something to do with refresh rate switching?

Hm not sure what the default setting is but I will try playing around with that and see if it makes a difference. I am also going to try taking the receiver out of the picture to potentially isolate the culprit.