Comment 1 for bug 1914415

This looks like it might be an issue with the postgresql charm. Possibly a missed expectation on ordering of events (it seems like it thinks there should be a dict already holding information during relation-changed.)
I'm not sure what that expectation is, nor why waiting would make it more reliable.
Maybe the postgres operator is coming up and not able to see its own workload by the time the relation comes in. It may be something that needs to be deferred, or something that is waiting for some other piece of data to progress.