From what you have posted I would say that some of the downstream power levels are too low below -6 and that is what is causing the problem, one thing I would do would be to go around and make sure that all coaxial connections to all VM equipment are finger tight best way is too undo the connections and then re-tighten, power off the hub again for 30 secs and then back on. If that doesnt resolve the problem then an engineer will be needed to correct those power levels.
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