Message SAP WRF_REF124 - &4 Error during conversion of module number in BAdI

Diagnosis
The system has created a new reference module number and has called aBAdI that converts the new number. An error occurred during thisconversion.

System Response
The system cannot create the new reference module.

Procedure
Check your implementation of method CHANGE_ID (BAdIFRE_MCH_ID_MOD_BADI).