Bug severity: seriously ruining my life.
Try to use korganizer to create a calendar entry when the server is not reachable (say, you are offline, or you typed the wrong password), and you may find that you end up with no error messages, an entry that shows up perfectly fine, but that will never be synced to the server, ever again.
I use korganizer, radicale and caldav for important things. The practical ramifications of me inserting entries in korganizer, seeing that everything looks ok, and then not finding them on my phone while on the go, are scary.
Think of things like importing .ics files with flight schedules, entering tax
deadlines, time and places for customer meetings, time and places of arrival of
loved ones I'm supposed to pick up.
I spent time setting up my own infrastructure for this exactly because I care that all of this works reliably.
And now I urgently took a morning off work to find a way to detect those entries that Akonadi is refusing to update,
The whole thing is cumbersome to run, but if you are using kdepim-based tools to manage your calendars and sync them across devices, you may want to give it a go every once in a while.
You can find the script and the notes I took so far on the issue at https://github.com/spanezz/akonadi-workarounds.