I have an unusual problem, I haven't been able to find anything on the issue.

When driving, the speed will not update unless the car hits certain RPMs. The light will flicker, and the speed will update around 1100 RPMs. It also updates at 2000+ RPMs. Idling, everything is fine, no flicker, but the speedometer may be stuck at a previous speed.

I pulled the dash, opened it up and cleaned small amounts of corrosion. Didn't really see any bad solder points.

I've followed the speedometer cable, in front of the battery. No signs of damage, however, I see where it goes into the transmission. My transmission is a little leaky, even around where the speedometer cable goes inside, but I'm not sure if the screen flickering/not updating has anything to do with where the cable goes into the transmission.

Here's a video of the issue:
https://streamable.com/1t9yd3

Thanks in advance!