Hi, I had that very same problem on my lens. I was told that it was "normal." It's not. The fix is simple. It's a matter of removing the "beauty ring" and then carefully tightening the small screws that secure the switch. I'm a clutz, so I had someone more skilled do it for me. It was a quick repair.
Don't let it go too much longer. You don't want any of the screws to fall out, which may cause damage. Shel > [Original Message] > From: Pawel Bartuzi > May I have a question regarding SMC K 18/3.5? The question is: is it > normal for this lens to have a slightly loose internal filter switch > (together with external filter thread)? There is approx. 1 mm of "play" > in my example - the front element however is stable and doesn't move. > > If it is not normal does anybody know if there is an easy fix for the > issue?

