I know my planter is different, it's a 2006 Kinze 3600 finger pickup, but we just went through this with it.  Had a lot of problems with singulation and doubles and didn't know what was going on.  My grandson found a drive that was "jumping" and found a couple bearings going out in part of that drive so we replaced all of the bearings in the drive and then it worked like a charm.  Singulation improved from 80+% to 99+%   all just from changing the bearings.