I've been having a problem where chunks seem to be "forgot and randomly regenerated" until a server restart. This has been happening since 493, but I'm on 522 right now and still getting the errors. I've associated it with when a backup is occuring (not always though, because I do a backup every hour, but the problem only ever manifests while doing a backup not any other time.) It happens about once or twice a day. In the console I get a large list of errors starting with the following and then repeating with a lot more null pointer errors (three of them are at the end of the small sample at the end of this post). I believe the critical point of discussion is this: I perform a save-all, wait for confirmation it saved, then issue a save-off command, wait 5 seconds, then start the backup (with 7zip if that matters), wait for the backup to finish, then issue a save-on command. The null pointer errors persist past the save-on command (along with the chunks appearing to be "reset" in-game.) When I restart the server, everything acts like it never happened and the chunks are back to what they were before the problem occured. Is it that Bukkit is not respecting the save-off command? Or is it that since there is no confirmation of the save-off command completing, it might still be finishing saving to clear the cache and I don't know? It's why I added a 5 second pause, but this latest error you can see almost 15 seconds after the save-off command the problem occurs. HALP!