After initializing a new CRA I noticed a FOUC issue out of the box.
I uploaded the app to S3 to see if the built application would have the same problem and the issue was gone.
Has anyone seen this and know of any fixes? I've spent some time looking into it but haven't found anything helpful. It seems to me this shouldn't be happening on an untouched CRA.
I have experienced the same problem as you got and take a look around for workaround and they say that only in the development mode will have this issue but the production works just fine!
Take a look in here: https://github.com/facebook/create-react-app/issues/6399