It's the TTL of the record in the public DNS, how the record is registered there is important. The record seems to have a TTL of 5 minutes, you can cache all you want... But it the public record has a TTL of 5 minutes and it changes, then it would be nice if you received that updated record instead of trying to keep on to a possibly outdated record ;)
Like I explained, the website has a TTL which is configured by the company hosting it. They set it to 5 minutes for example, if they change the ip-address of the website.. Then you will have to wait 5 minutes max for it to be in your DNS server when requesting.
My advice; Open a Microsoft Ticket and let them work on your issue, your trying to fix/change things but the real issue why this is happening is not being solved now ;)