Hello,
First and foremost, please gather detailed errors from the logs on the server side using the following tcodes:
1- SLG1 -- application log
2- SM21 -- system log
These logs should provide a more detailed error message. If you are running MDX on HANA you may get the MDX query if the error occurs after the MDX query is generated. You can capture the MDX query, if it is generated, it in SLG1 or UJSTAT. If you don't find any query, check for system dumps as well. I have also been able to capture detailed SQL statement errors in the system log, SM21.
After capturing the detailed error you can have a better idea what to check next.
Best Regards,
Leila