insufficient privilege during select

Hello,

we are trying to execute a select on a hana column view created by sap bw.

Select Statement from bo explorer:
SELECT "ZX_PROJAH" AS "ALIAS_0412B065" , "ZX_CUSTOM___T" AS "ALIAS_7EB67647" , "ZX_CUSTOM" AS "ALIAS_EE0FEF92" , "ZX_PROMON" AS "ALIAS_0412BD60" , "ZX_PRODGR___T" AS "ALIAS_2E5B30D8" , "ZX_PRODGR" AS "ALIAS_04129AA3" , "ZX_COUNTR___T" AS "ALIAS_A0478319" , "ZX_COUNTR" AS "ALIAS_EDBC3564" , SUM("ZX_REKLA") AS "ALIAS_67F03444"  FROM "_SYS_BIC"."system-local.bw.bw2hana/ZX_CUBE01" GROUP BY GROUPING SETS LIMIT 26 MULTIPLE RESULTSETS  ((("ZX_PROJAH") ORDER BY ALIAS_67F03444 DESC ,ALIAS_0412B065 ASC ),(("ZX_CUSTOM___T", "ZX_CUSTOM") ORDER BY ALIAS_67F03444 DESC ,ALIAS_7EB67647 ASC ),(("ZX_PROMON") ORDER BY ALIAS_67F03444 DESC ,ALIAS_0412BD60 ASC ),(("ZX_PRODGR___T", "ZX_PRODGR") ORDER BY ALIAS_67F03444 DESC ,ALIAS_2E5B30D8 ASC ),(("ZX_COUNTR___T", "ZX_COUNTR") ORDER BY ALIAS_67F03444 DESC ,ALIAS_A0478319 ASC )) WITH PARAMETERS( 'locale'='de_DE' )

Create Statement of HANA Studio column view:
CREATE COLUMN VIEW "_SYS_BIC"."system-local.bw.bw2hana/ZX_CUBE01" WITH PARAMETERS (indexType=5,
  joinIndex="SAPETB"."/BI0/SCALYEAR",
joinIndexType=2,
joinIndexEstimation=0,
  joinIndex="SAPETB"."/BI0/SDATE",
joinIndexType=2,
joinIndexEstimation=0,
....

We are using the user ROEMER to execute the statement.

The user ROEMER has following
granted roles:
- modeling
- user
- public
- AFL__SYS_AFL_AFLPAL_EXECUTE_WITH_GRANT_OPTION
object privileges:
- _SYS_BI grantor _SYS_REPO
- _SYS_BIC grantor SAPETB
- _SYS_BIC grantor _SYS_REPO
- _SYS_BIC grantor SYSTEM
- _SYS_REPO grantor SYSTEM
- REPOSITORY_REST grantor SYSTEM
- ROEMER grantor SYS
- SAPETB grantor SAPEPB
- SYSTEM grantor SYSTEM
analytic privileges:
_SYS_BI_CP_ALL

As you see, we have tried many combinations of SCHEMA and USER with the GRANT Statements
GRANT SELECT ON SCHEMA <SCHEMA> TO <USER>;
GRANT SELECT ON SCHEMA <SCHEMA> TO _SYS_REPO WITH GRANT OPTION;

Anyway we get the error of unsufficient privileges:
Could not execute 'SELECT "ZX_PROJAH" AS "ALIAS_0412B065" , "ZX_CUSTOM___T" AS "ALIAS_7EB67647" , "ZX_CUSTOM" AS ...'
SAP DBTech JDBC: [258]: insufficient privilege

Which privileges and roles are neccessary?
What is missing?

Best Regards
Andreas