I think DNS is the right suspect. The only other thing I can think of is to disable ipv6 on whatever network device you're using for internet. Especially where vpn is concerned, I've seen continuing problems where both are enabled. The wifi and wired ethernet ports are 2 different network devices on the same computer, and so is the pseudo-device used with the vpn. You could potentially disable ipv6 on all 3 devices on your machine. https://answers.uillinois.edu/uis/page.php?id=99981 (assuming you're on Windows)
Technical aside: With vpn, I've also seen a different problem with "collision" in ipv4 addresses, due to the home user's internet service provider using a local internet address that happens to also be used by your employer in their corporate network (behind the their vpn), leading to some communications just disappearing into a rabbit hole of undeliverable packets. There's nothing easy to be done about that problem. Either the employer or the isp has to use different "local" ip addresses, or the whole world needs to switch to ipv6.
no subject
https://answers.uillinois.edu/uis/page.php?id=99981 (assuming you're on Windows)
Technical aside:
With vpn, I've also seen a different problem with "collision" in ipv4 addresses, due to the home user's internet service provider using a local internet address that happens to also be used by your employer in their corporate network (behind the their vpn), leading to some communications just disappearing into a rabbit hole of undeliverable packets. There's nothing easy to be done about that problem. Either the employer or the isp has to use different "local" ip addresses, or the whole world needs to switch to ipv6.