Weird Honda speedometer problem?

I have a 1990 Honda accord ex with a 94 accord vtec sohc f22b JDM motor in it. Fount out later the car was converted from auto to manual. Anyway when I bought it the speedo didn't work so I replaced the speed sensor an still nothing. But later on I hit a bump on the highway an now it just jumps randomly as I hit bumps on the road. I've checked the wires to the sensor an there good. I'm not a big Honda guy so I was wondering if anybody might know what to start looking at cause i don't know where to start since everything was basically swapped out before i bought it. Any knowledge would be good.

There's a video on you tube how to fix this on your car hope this helps