New Relic is a software service that helps you manage your cloud environment, I use it here for this server and for many of our cloud servers on AWS and RackSpace. But we recently reenabled it for this site and when we did, the AMP errors on this site skyrocketed.
At first, I didn't put two and two together and I wasn't sure why my AMP errors spiked in Google Search Console. But after our engineers dug into it, we learned that New Relic cannot be enabled on your AMP pages.
I got this alert from Google and checked and noticed a massive surge in AMP errors:
So I tried the validator, hoping it was a Google bug but it was not a bug:
I assume over the next several days the AMP errors will go away.
Update: New Relic now has a document on how to handle this over here.