Evil Odometer

The odometer and PRND321 on my 99 Sonoma started flickering a couple of months ago. A rap on the top of the dash would get it to stop. I took the instrument cluster out and could find nothing wrong. Last week the odometer froze at 97585 and would not advance - the trip odometer advanced but would reset itself when the engine was shut off. I removed the cluster again but this time I resoldered every joint I could - I even tightened up the cluster connector on top. Everything seemed to be OK until yesturday (after a sleet storm) the odometer reset itself to 000000.0 (nice I now have a 99 Sonoma with no miles on it). Later that day it went back to the correct reading. Is there something that I missed? Is there something else I should be doing? Any suggestions?