Sorry if this too obvious, but also check the condition and adjustment of the knives and rolls. I was having a similar problem with mine. I swapped the knives end for end and adjusted the spacing and it made a BIG difference.
Issue is the knives, I bet the front half of them is wearing down and creating a gap so they are doing more stripping then grabbing, pulling, and chopping. The knives are slotted so you can loosen and adjust them in, you don't want them touching, but do want them fairly close (don't remember spec off the top of my head, manual would have it I'd think). Swapping them end for end as suggested is also an option.
Could I ask where you are at that you are picking corn at 17% moisture at the current time?