When trying to open the subprojects linked to a specific project I get a 500 error

Document ID : KB000122810
Last Modified Date : 18/01/2019
Show Technical Document Details
Issue:
I am unable to open the subprojects linked to a project. As I try to edit the subprojects an error:
"Error 500 - Internal Server Error. The server could not retrieve the document due to server-configuration or other technical problems"

By looking to the app-ca.log file, I see the following exception that is key to this specific scenartio:

ERROR 2018-12-06 21:53:41,612 [http-nio-128.87.241.32-80-exec-4134] niku.xql2 (clarity:admin:6499278__AC2BFB4A-4CFE-48DB-A4EF-BA8F6FD299BE:projmgr.projectProperties) Internal Processing exception 
java.lang.Exception: Invalid expression qobj: com.niku.union.persistence.PersistenceException: 
SQL error code: 1427 
Error message: [CA Clarity][Oracle JDBC Driver][Oracle]ORA-01427: single-row subquery returns more than one row 
Environment:
Any Clarity PPM release
Cause:
The subprojects OBS association have multiple OBS units linked to.
The following query will allow you to identify the project OBS associations:
select * from PRJ_OBS_ASSOCIATIONS where table_name = 'SRM_PROJECTS' and record_id = 'internal project ID' 

It should return one value per OBS unit.
The error is caused because it finds multiple OBS associations where it only expects one.
Resolution:
  1. XOG out the project and check the OBS associations.
  2. Delete the undesired/wrong OBS unit value form the XOG file
  3. XOG the project in.
OR
  1. Delete from prj_obs_associations where table_name = 'SRM_PROJECTS' and record_id = 'internal project ID' 
  2. Now the project should open fine in the UI
  3. The OBS association is now blank. Re-associate the OBS unit through the UI