Thanks Kulbhushaan Raghuvanshi,

I agree that when something complex has happened a simple message that explains to them, and that it was something on our end not something they did, and how to recover is best.

Personally I try to avoid trying to make errors 'cutesy' using words like "Oops!", "Ouch!" or similar. When we try to add "delight", we can end up annoying users particularly if they are trying to do a critical task.