Check the app-ca.log, and see if you do not see a problem with your DB LINK such as the following:
ERROR 2018-06-28 13:08:22,695 [https-jsse-nio-443-exec-395] providers.DWHDBHealthReportProvider (clarity:admin:13381417__72DFC4BC-7A29-434D-B5EF-DC01EAFB7CEB:nmc.healthReport) Error validating dblink :PPMDBLINK
SQL error code: 12154
Error message: [CA Clarity][Oracle JDBC Driver][Oracle]ORA-12154: TNS:could not resolve the connect identifier specified
SELECT count(1) dblinkvalid from [email protected]
Resolving the link makes the application retry the connection many times which could lead to timeout.