I've been keeping this Tracker entry as up-to-date as possible with my experiences. When filed, we couldn't restore 2.2 backups into 2.3, which we got around by creating backups without user data, which then worked fine. Now, we can't restore 2.3 backups into 2.4 for the same reason (and with the same solution) with the added 'bonus' of receiving 500 internal server errors instead of the error mentioned on the Tracker post.
I can't in good conscience make the issue a blocker, as Moodle functions fine day-to-day, but the fact that we can only restore course backups without user data is a concern (the main reason we create these backups is for disaster recovery reasons).
I encourage anyone experiencing this to vote and comment on the issue on the tracker, as without raising it's awareness it will not be seen and won't be addressed.