hello ljg45, this is likely caused by an outdated extension in your firefox configuration. in order to test that, you could try to launch firefox in safe mode once and see if the issue is reproducible there... [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems]] in this thread a few other affected users have named addons which were causing this problems for them: https://support.mozilla.org/en-US/questions/1041290