My Sky Q box turns off when I switch the receiver to its input

[Alex4D]

After I needed to move my Sky Q box to get better WiFi reception (it is much more fussy than my £20 Roku stuck), it now turns off my receiver when I switch to the Sky HDMI input on my receiver. 

It is a 15 year old Yamaha that has been working fine recently with the Sky remote controlling its volume via CEC. 

I've tried unplugging both. Plugging one in, then the other. The problem persists. 

Any ideas?

[Alex4D]

I also tried two different HDMI cables. 

I don't have the pink one that usually comes with the Sky Q box because it was a replacement of an old Sky Plus box, so the engineers just switched out the box - leaving the cables as they were. 

I also tried connecting the Sky Q box to a different input on the receiver. 

[Alex4D · Accepted solution]

Turns out this was an receiver problem. 

There was some sort of short on the centre speaker. 

I found this was a problem by first trying to switch to the Sky Q HDMI input with the sound fully turned down. The receiver didn't switch off. 

This meant that the problem wasn't the Sky box sending a 'Turn Off' message via HDMI. It was a short in one of the speakers that activated if the volume was set to a normal level. There is a a protection circuit in the amp to protect against shorts. 

By process of elimination, I found it was my centre speaker. Luckily the other speakers are OK. 

That's it.