Oracle Scheduler Jobs not starting the execution until 15-45 mins after scheduled time

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DB - Oracle 12.2.0.1 2 node RAC with multitenant
OS - Soalris SPARC 11.3

We have come across this strange issue where DBMS_SCHEDULER jobs were submitted, it just waited randomly for 15-45 mins without doing anything. Then suddenly it started and executed in the expected time. This happened with random scheduler jobs on different times. When going through the session details, they were waiting on 'PL/SQL lock timer' event. Also when we have come across a hardware maintenance and running on single node of the RAC the scheduler job delay was not occuring.

After opening a SR with Oracle and going through multiple SRDCs (Doc ID 2077171.1, Doc ID 2077182.1,  Doc ID 2077187.1), and looking through different bugs (Bug - 21047218 - Scheduler Jobs Hang For 23 Minutes Randomly Then Resume) finally we come across the actual culprit,

Bug 28402823 : 12.2.0.1 In Rac Dbms_Scheduler Set Schedule_Type To Null After Job Ran Manually

This one was kind of odd and was bit difficult to pinpoint as well. The fact the issue was not occurring when the RAC was operating with one instance was a main observation in troubleshooting.

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