This may be a silly question, but how do I know it is working properly? Apart from the fact I have (hopefully) connected it correctly in accordance with the instructions and haven't experienced any snaking, is there any way you can check its operation? Someone told me that they sometimes "groan" when turning, but the operating instructions (p36 7.2) state "the friction linings do not make a noise when driving...", It is a brand new unit on a new caravan and the paint on the tow ball has been removed.