If you use
Bugger or BugSack you can go back and look at past errors (that have occurred while they were enabled). Might be worth installing if the error only happens sometimes. Third-party error catchers also have the advantage of not popping up in your face while you're in the middle of a raid or other inconvenient situation; they can notify you with a message in chat, or by changing the color of the icon on their Broker plugin or minimap icon, and you can look at the errors later when it's more convenient.