457 Deduction not taking full flat amount

Update to this post. We are still experiencing this issue however we are closer to understanding exactly why. 

We allow employees to defer final payout of PTO hours & earnings to a pre tax savings plan. However, these earnings are not eligible to add to the RET special accumulator we have setup for MOST earnings. it's a Teachers Retirement System rule. 

I understand the reason these deferred PTO earnings are not allowed to be deducted to the 457 or 430b plans. Because the savings plan setup and the limit for those plans all use the RET accumulator. 

IF it's early in the year and the person doesn't have the sufficient earnings balance in the RET accumulator- then only a part is taken.