My building has lousy grounding.
Yes, industry learned a hard lesson when business systems installers grounded to the nearest fire sprinkler systems and that industry moved away from having the water supply heads loaded with water at all times...bad things happened man, bad things!
I also added new receptacle{PS Audio} with an extra ground line to the receptacles box. For me these made a great difference, especially on my noise floor.
If you can - and certainly for new builds/construction - I generally recommend dedicated circuits with isolated grounds be receptacle. The cost at build is negligible and can be worth cost later
Sadly there's no easy fix for such issues. Only process of elimination. Sometimes multiple fixes are necessary.
Agreed...but that is part of the fun isn't it? LOL
