Servis C60 Mower Adjustments

I have an old C60 Servis belly mower on my 53 Farmall Cub. (Three Blade Finish Mower, looks like a woods clone of a sort, 60 inch cut). It works very well, the cub pulls it fine and is strong, but I do have one small problem with the deck. The thing "stripes" one small line of grass between the middle and right blade, meaning it leaves about a 6 inch stripe of barely touched grass on the right side third of the mower.

I have swapped the blades around and the problem remains in the same location, right 1/3. I sharpened the blades, etc. The pulleys and spindles are well lubed and turn freely, the belts tensioned equally. The belts are new. HELP! This is driving me nuts. My final cut on my feilds (12 acres) looks great except for the stripe of grass left in each pass! This is driving me nuts!

Respectfully, Tim Leslie
A Vermont Small Farm