SAP Message AJ026 - Internal error in form &1 (function module &2)

Diagnosis
An internal error has occurred in form &V1& in function module &V2&.This is probably a programming error which you cannot resolve.
Note: the field &V3& has the value &V4&

System Response
The processing of the function module must be canceled

Procedure
INCLUDE ISU_SAP OBJECT DOKU ID TX

158244AJ026 in REGISTERS_ANALYZE (FM ISU_IPK_IMP_CREATE)
163481Term. of billing after change to register category