Radio interference with the NES and Retrotink 2X Mini?

[accaris]

I'm having a weird radio interference-looking issue with my NES front loader over composite and the Retrotink. I can notice on solid colored backgrounds, especially gray and blue, oscillating, wavy diagonal lines that look very similar to RF interference. These are NOT jailbars; I'm aware that the NES front loader has faint jailbars, but this is a different issue. It's not the Retrotink either, because it doesn't happen on the test pattern at all.

I switched from the OEM PSU to a Triad Magnetics PSU with an attached ferrite choke, and that didn't help.
I'm using the Monoprice Onyx series RCA cables which are copper core with double-shielded copper braiding. A very short run, 3-ft. only.

System is stock and hasn't been recapped. It's not a MAJOR issue, but it is noticeable enough to be annoying. Any ideas?

[Spacemonkey]

I've seen that in front loaders when the caps inside the RF box leak. I should note on composite video, don't have a retrotink.