I think the issue is with BISystemUser not able to impersonate.
One solution that will certainly work is to grant permission impersonate user and queryuserpopulation to
BIAdministrator role. At certain times the association of these two permissions to BISystem role may not work they they have this permission.
To add this permission to BIAdministrator role, go to EM
select obi stripe and click the blue arrow.
now click edit
search and add from oracle.secutiry.jsp.resourcePermission the below mentioned permissions
grant them as _all_
then regenerate GUIDs. Let me know if this doesn't work. next time paste nqserver log.