Have you tried running Firefox in Safe Mode for sometime to see if you have the save issue. https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf It's been awhile.... since I booted my mac.... it's been awhile... LMAO I have not been on my mac running 10.13 in a few weeks. Let me get on it and use it for the next hour to see if I have any issues.