Missed deferral opportunity--wrong definition of compensation

[jkharvey]

The employer has an ACA. They changed payroll providers and for two payrolls the wrong definition of compensation was used when computing the elective deferrals. The payroll company did not properly take deferrals from the overtime compensation. I know this is a missed deferral opportunity correction, but would it fall under the ACA rules or the non-ACA rules? I'm referring to the correction methods in the Revenue Procedure 2015-28. I question it becuase the error wasn't directly related to the implementation of a new enrollee for ACA purposes.