I noticed whilst playing with the 85/1.4 that if I turn the focus ring when the lens is in A mode there is a click and then the focus ring locks and won't move. I have to move the lens switch to M so that the ring will rotate again. Is the lens designed to do this and does it damage the lens if the focus ring locks like that? I find that I am gripping around the focus ring when holding the lens and sometimes it accidentally moves a bit and then locks. Thanks.