A self inflicted problem with syncthing
Cause: In Brave Browser Shields, disabling cookies also disables local storage.
Fix: Disable Shields for your syncthing install, or enable cookies
The error showed up as all rest/* routes returning 403 Forbidden. Angular kept printing this error so that was what I focused on. I though I was experiencing a past CSRF error (Issue#3138).
I scrolled up to see when the 403’s started, and noticed the first error was different, it was an error message saying localstorage couldn’t be accessed. This is when I realized it was my browser settings.