Odd Network Latency Problem

So I have a very strange problem that I can't solve. I have amazing internet and its extremely stable and smooth...for 15 minutes at a time.

About every 15 minutes, I get a massive network latency spike that lasts for about 1-2 seconds where everything freezes, then it goes in fast motion to catch up and goes back to normal.

The spike never happens for longer than 2 seconds, and the spikes are always 10-20 minutes apart.

PC is new and very high end, and I have zero issues with graphics performance. My internet works flawlessly in all other games including PoE1. I've tried all the usual suspects including port forwarding.

I'm open to all ideas.