Sites? What OS? What version of Firefox? If windows, what security software? Do you have the same issue with Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf

e621.net Win 10 latest none yes

I tried portable librewolf and it has the same issue, so it's probably in the code.

It works for me in Firefox and Waterfox. see screenshot What security software?

I don't use security software. I only use goodbyedpi.

well i rebooted pc and updated everything and that solved the problem for now