Firefox
Troubleshooting
Firefox exception breakpoint
Try these steps:
Refresh Firefox
https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings
Turn off hardware acceleration
https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems?redirectlocale=en-US&redirectslug=Troubleshooting+extensions+and+themes