Vibration will do that. When you set it back you'll want to leave just enough room so you don't get any contact with your fletchings. I'd almost think you may have a bit of contact by the way your arrows are hitting the target. You also don't want too much clearance and this will cause added stress on your string and cables.

On my bow the cable guard is at between 1:30 and 2:00 o'clock. I've got less than a quarter inch of clearence but no more is needed.