Diagnosis
When accessing the function module FKKENQ_INTERVAL_SET the programauthor made one of the errors listed under "&V1&".
1 - They entered contract accounts and business partner simultaneously
2 - The upper interval limit is lower than the lower interval limit
3 - Neither contract accounts nor business partner were specified

Procedure
INCLUDE NA_SYSADMIN1 OBJECT DOKU ID TX

Procedure for System Administration
INCLUDE FICA_NA_OSS OBJECT DOKU ID TX