Go to about:debugging#workers and remove all "service workers" for twitter (these are persistent background tasks that, among other things, can act as proxy ser

Go to about:debugging#workers and remove all "service workers" for twitter (these are persistent background tasks that, among other things, can act as proxy servers for requests on pages). This will resolve the problem, at least temporarily. You can disable service workers entirely by setting about:config dom.serviceWorkers.enabled to false.