I dont understand where you tie your shield I have some confusion amoung US prevalent terms .Ground you said GND is this related to PE , when you say your cable runs from GND to GND 'O' My . Do you mean you connect your shield to circuit common at one place ,or
PE at one place .




Please note I mean::::

PE= Physical Earth => Earth Ground = place where you dig the Earth and place some stuff there and it gives you so much trouble .

Circuit common = 0v => Electrical ground which is internal to the circuit and always and always seperated from PE .


Kindly/