Since Windows Insider build 21318 (we need Insiders build for some WSL features), after a few minutes of usage characters start to disappear from the application : pages, menus, etc. Only Firefox triggers this behavior, but once it has started it propagates to other Windows apps. The only solution is to quit Firefox and any affected app and relaunch. Firefox is pretty much unusable at this point. This bug is very much alike the one reported here : https://support.mozilla.org/fr/questions/1313520 Restarting in safe mode doesn't change behavior : not related to hardware acceleration or add-ons. Tested with Firefox v87.0 and Nightly. I also checked the described behavior also happens on co-workers computers same model/same configuration (this is on a Dell laptop Precision 7550 with an NVidia Quadro RTX4000).