A lot of noise can happen at higher frequencies. If you can hear that high, it can make a lot of things sound "bright" or fatiguing when present. I can’t anymore so fewer things sound bright....certainly not Aja.
Are your components physically isolated from each other? From any other nearby transformers or such? FLiourescent lights? Dimmers? NEarby appliances/HVAC? All these things can induce noise. Or it could be present inhernetly in a component not working well. Is your streamer on a wired home network? Some say noise there can make its way into the sound. I use wireless wifi only. No brightness.
Not saying that is the case here....just tossing out possibilities.
Put a sound meter to work. Maybe that can detect something useful to know.
You had brightness issues with your low ceiling from the outset as I recall. That could also still be somewhat of a factor.
What digital connection is in play? USB? Coax? Optical? I’d try USB over the other two and coax over optical just to see if any differences there perhaps.