I don't think we're getting the full story.
I suspect the dealer knows what causing the center section to cut about a foot higher than the sides. It's likely because the center section is about a foot higher than the sides. The question probably is: "What's causing 'that'?"
Hydraulic cylinder stops?
Can wings float?
Or perhaps different style blades with different offset (and suction) give different results, exaggerated by the type of material being cut.
Or center blade pins have more slop and can angle up more?
Center gear box output shaft shortened? Center stump jumper same height as sides?
I know it's a wild stab in the dark, but there's a little known trick that sometimes works well in theses situations: It's called "try looking at it."
(Sorry... I know, I know... my wife loves this helpful suggestion just as much
) ....but seriously...start measuring.