Black screen when idling without TV being on


I have two boxes (S905 + S905X), connected to two different TVs (pretty old LG + very cheap chinese Manta).
Boxes run 9.0.2 and 9.0.3 CoreElecs.
On each box I first disable CEC in the Peripherals settings, upon installation.
I do not ever turn off boxes, only powering off TVs.

The problem is that when I turn on the TV - I see only a black screen, but TV is showing that HDMI is active, and I can ssh into boxes, they work as usual, uptime is more than a day.
So this happens with different boxes, different TVs, almost identical Coreelec versions.

Here is the dispinfo, when black screen captured:

dispinfo: -

Also, while being in ssh session, I have noticed this process eating a lot of CPU (while others where almost idle):

2553 root 9 -11 92012 3620 2672 S 100.0 0.2 2082:01 /usr/bin/pulseaudio --system --disallow-exit --exit-idle-time=-1 --disable-shm 

This happens not every time I turn off / turn on the TV, but maybe 1 of 3 times, so I have to unplug the power each time then.

I can add more information if needed.
Next time I notice it, I will also take dmesg and kodi.log, what else can be useful?