Use the new https://profiler.firefox.com/ https://profiler.firefox.com/ . It can literally tell you what can go wrong inside the whole Firefox architecture (In

Use the new https://profiler.firefox.com/ https://profiler.firefox.com/ . It can literally tell you what can go wrong inside the whole Firefox architecture (Includes network, webtension, firefox internals, page scripts and so on). My personal guess about it is about extensions, did you retry it again in safe mode? And if you suspect it is a issue in firefox itself, you can upload the profile and open a bug at https://bugzilla.mozilla.org/home https://bugzilla.mozilla.org/home , so someone more familiar with Firefox can investigate it.