Change Process - Version ID already exists for item - Custom External Id

Hi Experts,

Implemented Badi RPM_OBJECT_SERVICES and method GET_NEXT_NUMBER_FOR_EXTID to generated custom external id for item and item version.

Problem: When the item type is moved to the next level by change process, trying to create item version with project version.

Error: Version ID XXX already exists for item XXX and cannot be duplicated.(but the version is created for the first time)

Version: PPM 6.0

It is working fine if we create the version directly from the version tab. Please guide me.

Thank you.