What kind of speakers are you using? You should make sure that your pedalboard is plugged in to (as close to) the same outlet as your speakers/amplifier to reduce the risk of ground loops.
On the connections I thought that I was improving because I moved from several outlets to the powermax directly into a furman in my rack, but I’ll dig into it, I switched some things and it did improved, I agree, it seems sometimes electricity has a mind of his own.
The next step is to remove power from your board. If (as it looks) you’re just using Eventide pedals, they will all relay bypass when you unplug them, so you should still get audio through them.
I got the Space stombox recently and it just grew to an expermentation pedal board for sound design, my plan is 3 H9 and the space at the end, only thing I am also planning to add a jhs color box, to use pre and post.
Lastly, you can start removing pedals from the loop to track down whether it’s one specific pedal having an issue. Basically, the goal is to simplify until you find the one change that makes the hiss go away.
I will look into it