Does this happen with all tools in that menu? Start Firefox in Safe Mode to check if one of the exte

Does this happen with all tools in that menu?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.

https://support.mozilla.org/kb/Safe+Mode

https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes