Over the past few weeks, Firefox has had daily or even twice daily instant crashes, where it just disappears off the screen. If I set Firefox to warn before closing windows, it has no effect, and no warning appears before it shuts. If I set Firefox to restart after a crash, then it will do so, restoring all tabs and windows, but you can still tell it has crashed as each tab will be blank when you click on it, only then loading the page, and any work in progress has been lost. I have updated Firefox, refreshed Firefox, and even started in safe mode, to no avail.

In "about:crashes" there is nothing shown in the past year.