Diagnosis
The system always checks if a business partner ID can be mapped based onan external object assignment. If 2 or more external assignments existsfor 1 internal value, a error message is written to the TTE trace log.

System Response
Processing terminated.

Procedure
If an external business partner ID should be mapped, proceed as follows:
Call activity: Assign Objects From ExternalSystems (Cross-Application Components -> Transaction Tax Engine ->Utilities -> Assign Objects From External Systems)
Select the relevant system: systemID1 &V2& systemID2 &V3&.
Check that the TTE internal value &V1& has a unique relation with theexternal value.
Save your entries.
Refresh customizing immediately with the activityImmediate Customizing Refresh.