Ben Admin processing message 000015 - Pay Calendar entry not found in pay calendar

Every year when we run Ben Admin we get the message 00015 - The pay calendar entry displayed below was not found in the pay calendar table.  The employees that are displaying in prep error  are employees that we loaded into our system for history purpose and were never employees of our company.  At the time of the data conversion we put them in a fictitious company and paygroup i.e. 999 (for both).  We do not have active employees assigned to either the company or paygroup.

The employees that get the error are different each year.  For the year in which the employee gets the processing message the Event Status remains in Open and Process Status Prep Error but then the following year their event status goes directly to Closed and Process status to Assn None.  This has been going on since we implemented Ben Admin and ran the first OE process in 2012.  So many employees OE event closed without any errors from 2012-2019 and now for OE 2020 they are coming up with the processing message 000015.