Mirror striking lens rear on Nikon?!

[GeorgeDexter]

A few years ago, in a camera store, I tried on a Nikon 35mm f2 AI on my D200. It mounted fine, metered, and gave focus confirmation, but when I fired it, I noticed something odd. Instead of the usual sharp shutter snap, it made a slightly dull thud, and the lens seemed to jump ever so slightly in my hand! I couldn't be sure. It wasn't overt, and it took the picture fine, but it kept me from buying the lens. I've since moved t the D700, and use it occasionally with AI and AIS telephotos without issue.
Recently, I had an opportunity to shoot a friends' D300 with a Nikon 50mm f1.4 AIS on it. Same thud and slight jump! Has anybody else experienced this? I examined the rear of the lens and the mirror, and can't see any signs that they're hitting, but there's definitely something wrong here.

[Sevo]

Sure it is the mirror? IIRC there an issue with the aperture lever torque between older Nikkors and some Nikon DSLRs that manifests itself in a similar way.

[GeorgeDexter]

No, I'm not sure that it is the mirror. It was just a hypothesis. I'd like to know more about this aperture lever torque issue, like: can it hurt the camera or lens?

[gaeger]

I've used lots of Nikkor AI and AIS lenses on a D50 and D300, and I think I know what you're talking about. The coupling isn't nearly as smooth with some of these lenses as with full-on digital lenses, but it's not the mirror that's the issue.