I am having this same issue. I have verified the T4 is entered correctly multiple times.
On line 44800, CPP overpayment shows $115. On line 45000, EI overpayment is zero.
Total amounts for CPP and EI paid on T4 total less than $750, so it seems impossible to overpay by this amount in my case.
I think there is a bug in the software.
