OData 503 Error

Hi 

I have a dataflow below that errors with a 503 error timing out. This has been working previously for a few years and was taking approx 3 minutes to run. It works with a premium account. I have set the timeout to be 1.5 hours but the timeout does not seem to make any difference.

I don't want to change all my users to premium, but would like to know why it is failing on one and not the other when it does not take a lot of time to run. I have other Odata queries which have the same issue.