My ZM 35/2 is the same as yours at f2. Looking from the front can see little bit of the aperture blades but look from behind cannot see any. I suppose it is alright and we do not need to do any thing.
can put some LocTite on it. Use the "blue" loctite
My 35f2.0 shows the same thing. As for the loose lens barrel - check the retaining ring at the back of the lens (small ring surrounding the back element).
... As for the loose lens barrel - check the retaining ring at the back of the lens (small ring surrounding the back element). There are two "notches" in it and carefully push against it ( as if you were unscrewing or tightening the ring). On the Zeiss lenses these rings can work loose and the lens assembly "wiggles" a bit. Tighten it if it is needed and it should cure the problem.
when I change the direction while focussing it feels a bit loose too.
How much play is normal for the zeiss lens, do I have to send it to Zeiss service?
Same issue with the loose focusing ring and infinity and this pisses me off... Even my "cheap" summicron-c focus way smoother. It really is a shame for a lens i bought 600€ used. Focus seems right but im not very happy using the lens. Sad
Yes, but I find me forgetting this while shooting. Thus my Biogon 35/2 is traveling to Zeiss (with my ZI body warranty issue) with a inquiry how much fixing would cost.