Intermittent 503: Service Unavailable responses

[Tech Contact]

Hello,

I'm seeing intermittent 503 responses to print requests made from a US production machine. The problem also occurs on an EU production machine (same user) but at a significantly lower rate.

The problem started appearing last month and so far the only noticeable pattern in the error is it appears to be tied to the volume of requests being made. Previous similar posts in this group suggest this could be a problem with the number of requests being made from one user. Is there a hard quota to how many requests can be made in a time frame? How do I confirm or deny this is the problem and what is the solution? 

Thanks!