I believe we have the more or less universal shower head holder where you loosen one end by unscrewing it to set the height of the shower and the other end holds the shower head. The end that holds the shower head has become very loose and I can see a Phillips screw in the centre but turning this seems to have now effect and it is still very loose and wobbly. Am I missing something obvious ? This is a new van so don't want to damage anything before referring to the dealer, but if it is just a simple task to tighten it can do it myself. Many thanks