I've come to dread the times I need to update Firefox on my Mac. Every time it goes through the motions OK but then it stalls, leaves a couple of zombie processes both called 'firefox' (that I cannot kill because they do not show up with ps) so that I cannot reopen Firefox. Moreover, a normal shutdown then hangs as the Finder tries to close them but cannot (at least I suppose) so that every reinstall necessitates a forced shutdown. With every update, either of Firefox or Macos I hope the problem has gone away, but it's still there. This is not how things should be. What is the problem here?