Xerox 800 - curved smudge / mark in black at tail of sheet and color loss at tail of sheet

Hi all.

I have a Xerox 800 ColorPress

I am running a short sheet 11 x 15 (12 point - 225 gsm). At the center tail of the sheet I am getting a curved mark.  It doesn't seem matter which side of the sheet prints first and it's always in the same position at the tail of the sheet.  I removed the curved shield over the IBT belt and it stops the mark but the 2nd BTB belt shreads itself.  So the sheet is definately bumping that shield, but how do you solve it?

Also, I am losing color at the very tail end of my image (within the last 1/2" of the sheet).  I tried to move around the value of the 2nd side bias in the advanced paper properties which helps but doesn't cure the issue.

I also tried tricking the machine by telling it my paper was thicker than it actually is.  The problem doesn't go away and I start to lose image quality elsewhere.

Any ideas?   I have a lot of paper to run.

Thanks for any assistance.