P20, audio thumps with HT system, Chord monoblocks and PJ hdmi cables

Power Components
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I’ve been trying to isolate and resolve a problem with my Theatre system this last 6 weeks or so.
Changing content, (Netflix / Prime), exiting platforms and disc playing all cause a series of audio thumps during these processes.
These thumps sound like they are coming from the center channel but both amps are producing them so it appears to be the center channel.
I’m in the UK.
I’ve narrowed it down to the following.
I’ve all my components plugged into my P20.
Having everything powered by the P20 gives a common earth so no hum.
The system includes my two Chord monoblocks which are used for music and double as my theatre left and right front speakers due to the Chord pre-amp having an AV bypass function.
An AV10 is my processor and my source is a Panasonic 9000 4K player.
My Sony 4k projector is also plugged into the P20 via a long power cord.
I’m using FIBBR 15 meter hdmi cables
All components share the P20 earth so no earth loop hum.
Somehow the pj hdmi cables are reacting with the Chord monoblocks to produce the thumps.
I know this because if I plug the pj into a back wall socket no thumps, but I do get earth loop hum because the P20 socket and pj socket are not sharing the same earth.
Also if I have the pj powered by the P20 and remove the hdmi cables no thumps, (also no picture of course).
I’ve also run the system with a TV as the display and no thumps because the pj’s hdmi cable is not involved.
(I’ve two identical FIBBR cables and both exhibit the same issue so I don’t think it’s a hdmi cable fault.)

Interested in any possible solutions to resolve the conflict between the monoblocks and the pj hdmi cables.

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Resolved - Dac power cord causing the conflict.
In discussion with manufacturer in getting this fully resolved.

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A further update on this.

With further discussion from dac manufacturer I was asked to try the dac on a different socket within the P20. I tried this and after testing the music side worked fine I tested the theatre side and I was surprized to find I had no audio thumps.
Interesting the dac has worked fine while listening to music on the original socket after returning from repair approximately 6 weeks ago.
Additionally I discovered I had moved the dac power cord to a different socket within the same zone rather than selecting a different zone as I had intended to do.

I’m not sure whether this indicates there’s some sort of an issue with the original socket I had the dac plugged into but I’ll need to remember this oddity should I have to strip down and rebuild my system at any time in the future.