Has anyone had clients with strange DNS issues in the last couple of days?

I've had two clients both reporting issues with Outlook disconnecting from Office 365 and / or websites not loading or needing multiple refreshes.

Both cases were DNS either taking a long time to resolve or timing out.

Both were HG659's using the router as DNS and it in turn relaying to the DHCP issued DNS Servers from a Vodafone fibre connection.

In both cases I changed the routers to issue static 8.8.8.8 / 8.8.4.4 for DNS and its fixed the issue.

In the first instance I was wondering if its an HG659 issue with the relay not behaving for some reason but today its happened with almost identical symptoms.

Maybe its just two problematic HG659's - Coincidences definitely do happen in IT and I can't really see how something at Vodafones end would effect the DNS relay in the router but it did seem a little odd.

Anyone else seen similar that they've just jumped in and worked around?