The device was returned for evaluation and the following root cause activities were performed: ten (10) scopes were disassembled and evaluated in an effort to determine root cause(s).The following conditions were observed that contributed to image failures from the use of electrocautery.Impedance specification for the scope is not clearly documented in the design specification.Torque requirement was not specified in the design but is important because it compresses the nut and the cable to the d-shape flange.Torque on the lock nut is critical to achieve the impedance and ground bond necessary for the device's immunity to conducted and radiated emissions from nearby electronics.Current design does not provide feedback to the assembler to know when proper engagement of the cable d-shape flange to the d-shape hole is achieved.The design relies on the compressive force of the o-ring to maintain contact of the nut to the housing.Excess krytox/silicone at the location where it gets applied.Proper tool for tightening the nut was not consistently utilized.Oxidation in the masked surface of the housing prevents proper grounding between the housing and the nut to cable.Subsequent to the initial complaint analysis, additional investigation and analysis were performed as part of capa (b)(4) and hhe (b)(4).Based on the conclusion of the hhe that the risk level is not acceptable, a field action reportable to fda under 21 cfr part 806 is being initiated.Consistent with the recommendations in fda's 2016 "medical device reporting for manufacturers" guidance, this complaint is now deemed to be reportable.
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