Troubleshooting Speedometer/odometer

[powerdog]

I've seen many threads on this issue but I am not sure where my symptoms are pointing.
1994 FWD stock SVX L. This was my daily driver until trans went (FWD). It sat for a year or so.
Speedometer also died just before the trans went. Not sure if odometer and trip odo died with it (at that time, I assume so). Finally replaced transmission. Observing the speedometer/odo/trip with a GPS over the last few weeks it has been working intermittenly...Went from not working at all, everything dead, to recording mileage at approximately 66% of actual miles driven with speedo recording within 2-3 mph of GPS, then sometimes speed jumps 0-20 etc, you've heard it before. Got my emissions notice so I jumped in one morning, cranked it up and everything is working fine, perfect, speedo/odo/trip. Failed emissions, gas cap. ok new cap. passed emissions.
So, after having the cluster work perfect several mornings, seems like everything dies in about an hour, give or take, not real sure of the time. It stopped working completely again, finally I assumed, so replaced gauge cluster (which was unbelievably within 500 miles of the original mileage)
but speedo is still dead, and odometer recorded 3 tenths of a mile on a 1.7 mile distance as measured by another car. I reseated the VSS connector. No change. Did not replace the VSS. I see them online @ $100+ to maybe $250. Is the VSS the problem? While looking at the back of my original cluster, I noticed the screws on the speedo could be tightened a little which I did but not more than a quarter turn (in other words, they seemed ok). I did not check any screws on the back of the replacement cluster that is currently in the car. Current status: no speedometer and mileage recording way too low. Is the VSS the problem?