CORS errors

[officert]

I'm running into an issue with CORS when using Vercel Speed Insights and Analytics in a NextJS app:

The POST requests seem to work fine, it's only the POST + Preflight request that failing.

I've tried enabling CORS in a NextJS app as described here:

https://vercel.com/guides/how-to-enable-cors#enabling-cors-using-vercel.json

But it doesn't seem to affect the _vercel endpoint.

Do the _vercel endpoints block CORS?