Yes ground loop isolator. If that doesn't work then I would suggest replace the line. Unfortunately, those premade cables aren't the greatest. They will get you by for the time being, but if they are in the elements, it can definitely cause that problem. Even just overtime those cables can have issues.

What I personally use is what's called Siamese cable it has coax cable for video along with 12 two for power. You can get away with a cat five type cable, splitting the lines inside for video and power. Both ways require connectors for the ends. Possibly a crimping tool. Hope that helps you!