I had the same issue last year and just let it go... This year I investigated further. The general solution is to add an extra box 14 item for Retirement compensation using the Box 1 plus the Box 12 "D" total but this still produces the error. In my case I added Box 1 plus the Box 12 "D" plus Box 12 "GG" plus the Box 14 Tier 2 number and it comes out perfect. May have to go back a few years to make sure the Gov has it correct in their records..
