What connector version are you running? If possible, do install the latest version of the Qlik SAP Connectors. That should help you with the "mismatch detected"-problem.
The Report Connector internally reads two tables from the generated spool to handle the report rows. Sometimes these tables do not have the same number of rows which cause the "Mismatch detected" message to show. However, the latest version of the Report connector is capable of getting the relevant information and can therefore render the report.
For finding the version number, either look at the first few lines in a log file from the folder:
or the properties and the "details" tab of a .dll in
C:\Program Files\Common Files\QlikTech\Custom Data\QvSAPConnector
All the versions can be downloaded from the Qlik support.