Using a hasselbad lens on contax rts3

i have a contax rts3 and a hasselblad lens adapter, and several hasselblad

lenses. my problem is. when i put a hasselblad lens on the contax, and attempt

to use it in aperture priority mode i cannot use the widest aperture ie; 2.8, i

cannot stop the lens down without resetting the lens. if i only stop down to f4

it works fine closing the aperture properly to f22. at f2.8 it just stays there

until resetting. am i doing something wrong in setting up the lens?

thanx in advance

garth