Hi,

The coupling between the lens's aperture and the meter is done via a
small cable that winds up on a spring loaded drum (the drum's spring
brings back the aperture ring back to f2) under the top cover (rewind
knob side). The drum rotates as the cable is pulled or released and this
drum is connected thru gears with the FRE (famous for breaking),
integrating, via resistive tracks, 'info' from the ASA dial, exposure
compensation and aperture to the meter.
(I hope I'm using the right words and that this sounds clear... :))

What you describe looks like a problem with this 'cable'. It might be
out of its track, broken,... A problem with the drum is less likely (or
maybe is it stuck ?).

That should not be a difficult repair (read 'not that expensive') for
someone used to it...

HTH,
Karim