ARC Dolby Digital Plus failure with Yamaha RX-V375

[stu-e2]

I'm a proud owner of a new 65x95j. I am having a problem with Dolby Digital Plus (DD+) selected for the ARC connection to my trusty Yamaha RX-V375 AV receiver. If I select Dolby Digital (DD) it works. If I select DD+ the Yamaha goes silent and the display says "Decoder off" Which means it is not receiving any signal. If I then manually change the input on the Yamaha and then back again to the ARC input, it works. However I have to do this every time the TV is turned off and on again or when the audio changes to a different format.

I've tried different high speed HDMI cables including a HDMI Ultra Certified Cable.

I can also confirm DTS works ok via ARC.

The Yamaha has been working with a Fire TV stick with DD+ so this format is supported at least on a regular HDMI input.

[Csabi1984]

Unfortunately my strength is not English :)
Forget the STB device in my case.
I mentioned it because I read on another forum that similarly (another HDMI device affects the operation of HDMI ARC) while I think the HDMI ports shouldn’t affect each other, or do I know wrong?

[rooobb]

@Csabi1984 yes you are wrong. HDMI-ARC works only if HDMI-CEC is enabled and this one is affected by any component connected to the whole system: a known case for issues were/are Sky decoders that has a bad HDMI-CEC implementation that makes any other system connected to works incorrectly (for this very reason you may find adatper/cables HDMI CECless that can be used to exclude a single device from the chain (while still sending audio/video obviously)

[Csabi1984]

I read about the HDMI CEC-LESS adapter but I think if it is enabled then the ARC transmission from that device will also be off or will the audio pass regardless?

[rooobb]

Arc scope is limited to audio device only. And there can be only one connected

[Csabi1984]

I think CEC either works or it doesn't :). The fact that one day is good and the other day is no longer what I think is a software bug.
But we can talk about HDMI cables, which I also think that if it is capable of 4K60 Hz, it should last the next day :)
As a side note, the TV doesn't actually turn off but goes to sleep (if I know it)

[rooobb]

That's not always the case because CEC is only a simple one-pin protocol (pin 13 btw) but the underlying implementation can be quite tricky. In any case, in your case is quite easy: if pulling out the set top box solve the issue, you can try to use a cecless adapter to connect it and forget about the issue.

[Csabi1984]

I don’t have an STB device but a Dune 4K ProII media player and an Amlogic X96 maxplus. 
The STB box anomaly was for someone else with this type of TV.