Okay I have tried some more and I can some time, but only like every 5e time or so detect a very minor click through the headphones (still not really popping) then change from 40 to 39 and the same from 48 to 47. This never happens then I turn the volume up.
I don’t have any good explanation to this more than what I sometime detect as a very small relay clicking must be much higher in your M9, by reasons I don’t understands, and consequently make a popping sound. My Burson Soloist who has a higher level of click noise creates a bit of popping then changing volume. More so then going down than up.
Is the popping sound very loud and do you get it then using the remote as well?
I haven't actually tested it with the remote control, i'll do so on the weekend.
Regarding the level of the popping, it's dependent on the volume level, so when i'm adjusting between 0-30 it's not audible and then i start to hear it from 30+ and it gets louder and louder. as I go to 100. In all honesty it's not loud at all but I can still hear it, I guess it's because i'm not used to it. Almost like a scratching noise.