I actually found I had issues with the seat lock/latch when trying to refit the seat....If I pushed the seat hard up towards the fuel tank, I had trouble getting the lock to give that little "click" to latch....so I thought the same as you and had a fumble with the little harness/loom in the same area as the lock mech...to no avail..

After ten minutes of aimlessly fumbling around with it and looking for an adjustment of sorts etc...I finally came to the conclusion that if I fitted the seat and "didn't" push it too hard towards the front, it would latch every time

The adjustment and/or little harness had nowt to do with it..was just me being a twat...!

Smithy.