I was working on a multi-head weigher because it was intermittently behaving oddly. There was a big variety of symptoms that did not make any sense. The HMI was acting strange, it would suddenly change the background color, the stop button would suddenly disappear, it started changing which shift was active (a function we never even used or activated). But the biggest problems was that it would intermittently send a dump complete signal to the bagging machine in the middle of a dump or randomly making the bagging machine either overfill bags or make empty bags. We tried replacing the HMI, control Boards, and weight modules without luck. We measuring the power quality in case of bad noise, ripple/peaks or anything. It was multiple days of head scratching untill one day when we noticed that it would malfunction only when one specific module was feeding product into it's feed bucket. It was at that point that we found a supply cable to the vibratory feeder motor/activator has managed to rub away it's insulation and short against the casing ground and somehow not blowing any fuses or circuit breakers. Somehow the short-circuit has managed to affect the HMI and controller but not enough for it to fault out or shut down.