Whenever the instance is upgraded, a few of the scheduled jobs will not get processed.
The jobs which will not process include text index event processor, metric update event processor and report view event processor.
This is expected behavior in the platform.
There is flag call "Upgrade Safe" in every schedule jobs.
If the job is marked as Upgrade Safe (check box of 'Upgrade Safe' is checked), then it will run during the instance is upgraded.
If the job is marked as not Upgrade Safe (check box of 'Upgrade Safe' is not checked), then it will not run during the instance is upgraded. (Like text index event processor, metric update event processor eg.)
It is not recommended to change the upgrade_safe flag on any record to upgrade_safe=true.
All custom sys_triggers must be marked upgrade_safe=false.
The event processor runs during the database upgrade, however, only email related events are processed.
Email generation for outbound notifications and inbound email processing are both fired from events in the event queue.
After the instance upgrade is complete, all the upgrade unsafe jobs are processed and catch up.