What I did change was that after the 5.6 upgrade I manually started the server under root and not my personal account as previous.
Some (uploaded) files got the wrong user name (root) which lead to a backup issue. Can somebody help me in the right direction?
java.util.concurrent.ExecutionException: com.ebasetech.xi.exceptions.FormRuntimeException: com.ebasetech.xi.exceptions.FormRuntimeException: java.sql.SQLException: An SQL data change is not permitted for a read-only connection, user or database.