Take the first simple step again: replace cables, It is cheaper to change a 5 dollar cable than a 100 dollar gadget. While there may be many sources for corrupting your signal, a bad connection might be a probable cause.

If it is not the cable, the next step that I would take is: take that box to a different location in the studio, even if it means longer cables for the test.

Eliminate the cheapest and easiest accesible sources of noise first. It is not always the most expensive part, Murphy's milage may vary.

Desktop; i7-2600k, 8 GB mem., Win 10 Pro, BIAB 2017; RB 2017 - latest build
Laptop: i5-2410M, 4 GB mem, Win 10 Pro, BIAB 2017; RB 2017 - latest build