Lift sensor not working

I've been getting to know my Chamberlain LiftMaster Professional Formula I garage door opener. It was originally stuck closed, but I played with it and it eventually got stuck on the Stop Bolt. I took off the belt a couple times to loosen it up (it was always getting really tight between the motor and one side of the trolley and no matter what I did, it would continue to close.

Eventually I came across a great youtube video of how the lift sensors work so I took the housing off to look inside. The middle screw/gear that moves the lift sensor in the middle had popped off. I popped it back in, adjusted the up/down sensors on either side and ran a couple tests. In some cases it mostly tried to run past the up sensor entirely. In most cases, it stopped around there, but if I pushed the button again, instead of reversing direction, it would just continue in the same direction, eventually stopping after 5 or so seconds.

I inspected all the wires but didn't see anything pulled or striped. I then took each out and re-attached them (felt pretty snug to begin with). I also tried to tighten the other side of the connection where the wires meet the circuit board (although to be fair, I didn't remove the back wall of the housing so it wasn't the BEST attempt. Lastly, i popped the middle sensor out again to test the connections manually. I turned on the opener, and tried to manually touch the middle metal plate with either of the side sensors (for up and down), but it never stopped the motor from running.

Any ideas left to try? I suppose there's a chance my circuit board needs replacing, but I'd love to confirm it first cos they cost ~$70. Plus I partially question if its the board cos it does turn the motor on/off when i push the button and when I push the sync button the LED just stays green (I know this LED can blink error codes). I would greatly appreciate any help debugging the issue. Thanks!

 

]Either a broken limit wire or bad circuit board if you are manually touching the contacts and the motor keep running. It's usually the grey wire that breaks [ATTACH]102939[/ATTACH

 

Thanks for the response! I visually inspected it and it seemed intact and clean. I suppose i could try replacing the wire entirely (cos that'd presumably be cheaper), although it's tucked away pretty neatly and where it connects to the motor I think is a fancy multi-connector and not just the one wire... so that might be hard to do. Any other ideas would be greatly appreciated. Definitely wouldn't mind spending more time to test cos when I did a quick circuit board shopping search, seems like you need to buy the whole back panel (not just the circuitboard itself) and they aren't super cheap ($70)... so any testing I could do to confirm thats the problem would be great.