Exactly zoele! Happening with all devices I've checked. PS4, STB box and this cheap android box.
It works well with my old tely and my friend new sony TV.
After 2 days of testing I've found how to get picture from it but it's just workaround.
Box connected to TV powered on and never powered off.
HDMI where box is connected has to be choosen and then power off and power on TV.
Picture is ok and stays there till I change resolution or refresh rate which is nice feature in kodi to play files with different specs. When I lock kodi to display only one resolution and refresh I can toggle between sources with no hassle.
Another scenario. Watching TV from internal tuner and power off TV. Then power on and switch source to never powered off android box. No signal again. TV need restart on source from hdmi to display picture. And is little bit annoying to watch 60fps movie on 24p display

jerky as hell.
I'm not sure if I did'nt mess a bit with libFakeEDID. Can't remember really.
Even if I did will those changes get overwrite when installing new/older firmware in Tv?