Using audio isolation transformer to clean power to a Raspberry pi
Probably the black_brick power supply is your problem. Those supplies have a large capacitor (several nanoFarads) from primary to secondary, so as to pass the FCC interference tests. But lots of fast-edge trash also gets coupled from secondary to primary, and like all charges,

will explore and use ALL POSSIBLE PATHS to get back home

To block those charges, you need a common_mode filter, and possible differential_PI L+C filters (here &quot;differential&quot; means FerriteBeads in both

DC_GROUND

and in

DC_RAIL

Those black bricks are cheap, and you get the noise_supression you have (not) paid for. So you get to add noise suppression.