As predicted, removing system 7 (the unit that usually has worse rf) had no effect on the popping sound in other mics.
I plan to meet up with my foh friend and hand off a mic for him to try at his venue. Also a small correction: It was mentioned to use him as a line6 dealer to call line6 as a way to get more attention to this problem. As it turns out he is not a line6 dealer. He tried to become one, called line6 numerous times to inquire about dealership but line6 never returned his calls. So that avenue is not an option.