It's not just the red and green leads.
I'd unplug all the small green leads on the reel driver board too.
Spray contact cleaner into the end of each lead.
And at each end for the red and Green big leads.
the opto lights should light up when spinning.
If one stays on,that where the problem is!
This fault is usually only a bad contact.
The reel opto lights should remain off when
If you move a reel by hand then it will flicker on.
That will tell you that one works ok.
I have to do this with all my mpu3s every few months.
They run pretty sweet now.
Maybe a run over those pins with a fibre pencil may
also rectify this.
Hope you sort it Mike.