Everything in the same rack being feed from the same power conditioner and only a 2M cable.
I am 99.9% sure it is not EMI.

It still could be a ground loop. Is there a coax coming in for video service? If so, disconnect that from the rack temporarily to see if the noise goes away.

Impaqt seems to have experience with a problem that was very similar. And it is an easy check to do what he is suggesting. Might want to go with that idea 1st.