Yep - two from the interface to the behringer box, and another two from the box to your monitors.:wink:
You've already been given the answer several times mate --- you have a ground loop, spend the 20 quid on the behringer box that I linked to above,...
You have a ground loop between your monitors and interface. Get one of these: https://www.thomann.de/gb/behringer_microhd_hd400.htm and connect...
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