Weird CORS preslight response issue has just happened

Really weird but all endpoints are not working on load due to the following error.

Access to fetch at 'https://api.staging.avm-api.com/api/developer/dropdown' 
from origin 'https://igc.evalio.io' has been blocked by CORS policy: 
Request header field baggage is not allowed by Access-Control-Allow-Headers 
in preflight response.

They do work when I use the app after the page has been loaded

Strange how this only just happened but it was due to me creating a Sentry plugin 3 weeks ago.