When the distro updates Firefox out from underneath it Firefox's options are; crash because API call does not match, detect the API incompatibility and prompt the user to do a clean restart, or spend a monumental amount of engineering work to maintain API compatibility while running mixed Gecko versions.

Using the Mozilla build in /opt, the Snap [1] or Flatpack [2] versions will avoid the distro updating Firefox out from underneath it.

[1] https://snapcraft.io/firefox [2] https://flathub.org/apps/details/org.mozilla.firefox