Sometimes the backs can require new seals, or the frame spacing can go off. Greg Weber is the go-to guy for Koni repairs.
As Jan from Warsaw said, pull the wind knob out smartly to make sure the film is wound. Then push it back all the way with the heel of your palm; don't be too gentle. The mechanism is sturdy and can stand this treatment.
And he's right about rangefinder adjustment -- very straightforward. If memory serves, vertical adjustment is accessible if you remove the middle cold shoe; horizontal by removing the flat disc on the right side of the back of the top cover. Or, you can remove five screws (one is hidden under the film back) and the whole top cover lifts off so you can clean the glass and adjust the RF with plenty of room to manoeuver.
There are only four lenses -- the 58 (or 60, I forget which one came first; they're similiar but not identical, I believe); 90; 135 (rare); and 180. All are really good, though rather slow. The 180 is rather a monster. The earlier lenses are Hexanons, the later ones are Omegons. The later cameras, such as in Jan's picture, are called Rapid Omega (100 and 200), and the earlier ones are Koni Omegas. The R-Os (and Omegons) were made by Mamiya after Konica sold the production line to Mamiya. The Rapid Omega 200 and the Koni-Omega M (?) allow changing film backs mid-roll, while the others do not.
Enjoy the camera! It's really nice to use, even though it's a very different beast from the norm in almost every respect.
