After our upgrade, we kept a close eye on our monitoring alerts and noticed right away when one for workflow errors in the last day showed us this:
ORA-04061: existing state of has been invalidated
Reaching out to the team responsible for validating the release of the workflow, they weren't quite sure if this was a one off issue or a complete outage type of issue but upon further examination it was determined that the resolution to this was a bounce of the application tier. I was skeptical, but believed in what I was being told, and it just so happened we had an application tier bounce already lined up for another issue so the stars were aligned and the next day this error went away. I'm not quite sure what object was invalidated, as you can see that between of and has in the error message, there are 2 spaces as if the object name was not able to be reported up in the error stack.