It sounds like you are doing all the right things to track down the noise.
One thing to be aware of is that if a module is dumping noise into the system that same noise can present at the output of other modules!
This can lead to a cascade of noise build up, the one problem becoming more amplified as more patch points are connected to the outputs.
The first time I encountered this it drove me crazy until I figured out what was going on, it just so happened that I had one module with a screen that was generating noise (as they do) right next to another module that was very prone to picking up noise! Who knew!!??
........I took out everything else changes rooms in the flats etc. Thats sadly no the problem
had this with the black mixer of Erica synths, it was picking up noises of the modular
:) Thank u
j.manuel