Speedometer Problems

It climbs up then suddenly drops. The car is parked and its sitting at 35mph right now. I'll post a video tomorrow.

That points to instrument. I've been seeking parts to repair one with the same symptom for a couple days. In hand testing it would hold the needle up. In the owners car this was wild needle swings.
The needle return spring is as tiny and weak as a watch spring. It cant overcome resistance. There is still some hope though. If you get lucky you'll find debris including metal on the magnet in its gyro is causing the resistance. Good luck