Check the full headers. They should tell you exactly where in the chain the delay was.
Personally, I wouldn't worry about an isolated delay of that magnitude. There are many reasons why such a delay can be expected occasionally. However, if a significant proportion of the mail had similar delays, that would be a different story.
Please update your ticket if the issue still exists. Don't forget to mention the sender/ recepient if the email is not received yet. If received, please paste the headers.