WP users often run across the error that they are not allowed to post. Going back leads to an empty form. This error has been random and devilishly hard to figure out why,.
Some sites have several suggestions, all of which are useless.
Generally the error is transient, starting over usually results in a successful post. The lost content is not saved as a draft either.
As far as we can ascertain there is some permission problem with connecting to the database. For the most part MySQL is very stable and it is widely used in production systems.
Error logs are not very helpful so we are not at all certain why the error manifests.
One idea for WordPress is to automatically save drafts periodically so that if there is a problem all is not lost.