I noticed today while turning the iris ring it seems almost at certain points like a grain of sand may be under it or something.,..it drag a bit gritty. I didn`t have any issue last i used it, but when I took it out of the bag today it had a little bit of crunch to it. Is this normal? Or did some micro grain of something sneak its way in? The zoom ring drags a little sometimes which i figure was normal, but you can tell its the ring on the plastic underneath, the iris really seems like theres something else