CORS error in Firefox (Chrome works)

For my Cloud project with Next.js,I am getting CORS errors when attempting createDocument(), but in Chrome it all works fine:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://cloud.appwrite.io/v1/databases/***/collections/***/documents. (Reason: header ‘user-agent’ is not allowed according to header ‘Access-Control-Allow-Headers’ from CORS preflight response).

I am new to web development and wonder if there'n an easy solution for this? Maybe it's a browser configuration on my side, but a friend of mine who I asked to test it said that nothing happened, so I assume he also had an error in the background.

Again, Chrome works as expected with no changes to the code or Appwrite console🤔

I inspecter the Request Headers in the Browser Networks tab and it seems as iif Firefox doesn't sent the specific headers.

In Chrome, I can see the 'X-Appwrite-Project' and so on headers, but in Firefox they are not there. Could this be the issue?

And does anyone have a solution for this? AFAIK I have no special Firefox setub with addons that could interfere here.

Will update here if I find a solution for it!

Screenshot of the networks tab and the request

CORS error in Firefox (Chrome works)