So I recently picked up a 16-35 II used. I checked the glass and the inside of the lens, and it was in extremely good condition, seems like the man hardly touched it, no signs of wear and tear at all, date code is uv so it is about a 5 year old lens. My concern is, I just got done doing my first shoot with it and I realized it makes a small clunking noise when it auto focuses is this normal? and when I move it around it sounds like something is a little lose inside. Does this happen with anyone elses 16-35? The lens also came with the blank warranty card, can I still use this even if its been 5 years old?