mysqldump is trying to lock tables and is failing due to an authentication issue of some sort. Try appending
Code:
--lock-tables=false
on the command, it may be a sign of a bigger issue but locking isn't manditory for a backup (and can cause ill side effects anyways, you should either shut down the server for safe backing up or not let the backup lock the db since you can get potential partial/corrupted pivot entries in db if the live server tries to e.g. back up character_data, fails due to table lock on backup call, but then backs up to character_spells and succeeds, you now have half-assed data entry.)
Another reason is if a script or task tries to lock a table and doesn't unlock it, it'll get stuck, you can manually unlock it if you know the table, or if lazy do a a mysql reboot to fix it.
If skipping the locking of tables does not repair things, some times if a db gets corrupted and needs to be repaired you can get odd lock messages, too, so a safe restart of the mysql instance and watching the logs could give signs of other symptoms not obvious. (You should be watching logs anyways to learn about the health of your DB)
~Shin Noir
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