Taxes for employee not taken on Supplemental Pay in interim, but taken in regular payroll

We have now had three instances where we created an interim for an employee for supplemental pay and no taxes (Federal, State, Local) were calculated, but these employees were just processed through a regular payroll cycle and the taxes were fine. And then strangely, several days later when we create an interim for supplemental pay for these employees the taxes do calculate. The Work Tax Area has not changed, the Natl/Fiscal Data has not changed, nor has the Tax Overrides changed.

Has this happened to anyone else?