Speedometer/Instrument Panel Issues

[dodge862]

The problems started about a year ago with a code for "P0720 - Output Speed Sensor Circuit". I noticed the speedometer would not register periodically and then rebound. No big deal. I researched and replaced the transmission output shaft speed sensor and no change. It wasn't happening super frequently at first but now you can't tell how fast you're going at all.

Speedometer issues

youtu.be

Since the sensor did nothing, and prior experience with sensors being that new ones don't always agree with the truck, I swapped the trans sensor back to the original as well as the rear axle sensor that had been replaced years prior for ABS lights (no change there either). Again, no effect.

Anyway, I recently remembered there is a test you can do on the instrument panel, something I did long ago for fun back around 157,*** miles.

Instrument Panel Test - Success

youtu.be

Assuming that is the case of a "good" test, that leads me to these next two tests could be conceived as "bad" tests

Instrument Panel Test - Failure 1

Potential instrument panel failure

youtu.be

Instrument Panel Test - Failure 2

Potential instrument panel failure

youtu.be

So I'm looking for a couple of things...
First, are my suspicions correct in that the last two video links show a problem with the instrument panel?
Second, could that be the cause of my speedometer not reading anymore?
Third, has anyone else had a similar problem, and lastly, what can I do to further diagnose/fix the issue (check wiring, replace gauges, etc)?

Thanks for the help!