*ist D with KAF lenses

I have a Pentax 70-210 KAF zoom which refused to work on my *ist. With the lens in 'A' mode the camera did not show the aperture setting. I suspected that the contacts between the lens and camera were not meeting so I dismantled this lens and another (a 50mm KAF) and swapped the bullet shaped contacts from one lens to the other. The contacts on the 50mm lens seemed to be longer than the ones from the zoom. The zoom now works perfectly and the problem has been transferred into the 50mm lens! Has anyone else had a similar experience wth dodgy contacts?

No direct experience, but I recall reading somewhere (maybe elsewhere in this forum) of a similar problem arising due to oily or dirty contacts.

Dirty contacts would give the same result. I've ended up by splitting the longer contacts that came from the 50mm lens so that both lenses have a long contact in the crucial position that provides the contact to tell the body that the lens is set in the Auto position. The "A" contact on the body side is different to the other contacts on the body and appears to be recessed compared to the other contacts. Presumably this is by design but the tolerances between the lens and body don't seem to be right.