i found the Solution: The default Layout Settings in SAP, controls which kind of field delimiter the Report Connector is used. If a sorting was set in the Layout-Settings, you will get a "5" as Delimiter otherwise a "!".
Very strange behaviour!
Hopefully I could help you.
There has been several cases reported with similar symptom to Qlik Support, but we have not been able to find any issues in the SAP connector. The common conclusion is that it is related to SAP side settings.
Michael's comment above is probably the explanation in this case, if it resolves the issue.