The wheel was double checked for tightness, so ideally I can discard that.
Also , it doesn't make the click, until I reverse again or vice versa, that's why I suspect the pads or at least one of them , has some slight movement when the brake is applied. hence the clicking sound !!
to me it also seems like one of the caliper pistons might be slightly seized , and does not have the full force until the pedal is actually applied. therefore the pad remains slightly loose , and that is why I hear the dreaded clicking sound ,......
thanks again