rpi3 hdmi sound problem

Hello all,
I bought a rpi3 a few days ago and set it up as Kodi media player (tried osmc and openelec)
In general it works great. However I found one issue with my set up.
I have PS4 connected to my TV via HDMI1, rpi3 kodi (openelec or osmc, tried both) connected to my TV via HDMI2, receiver connected to my TV via coaxial cable (digital input from TV).

Situation 1:
RPI3 hdmi cable is unplugged. I use PS4 through HDMI1. The sound goes to TV speakers (which are shit and I don’t want to use them) as well as to the receiver speakers through coaxial digital output from TV. All good

Situation 2:
Both PS4 and RPI3 are connected to tv via hdmi1 and hdmi2. I use rpi3 Kodi on osmc (or openelec, no difference). The sound from rpi comes to TV speakers only but not to the receiver speakers.

Situation 3:
Both PS4 and RPI3 are connected to tv via hdmi1 and hdmi2. I use PS4. The sound goes to TV speakers only. Not to the receiver. But as soon as I unplug the hdmi cable from the rpi3 receiver gets sound.

Situation 4: if I hook up my laptop to hdmi2 port instead of rpi3 both PS4 and Laptop work ok on receiver.

I reckon the rpi3 sends something to my TV over hdmi to disable the TV’s digital output. No idea what and how this possible.
Couldn’t find anything about the issue in the internet.

Could anyone give me a tip what It can be and how I can fix that?

Thanks in advance