The most recent ones that I ran into seem to have been fixed based on a quick check. mermaid.js docs site was one of them where nothing on the page was clickable (I think Firefox was rendering an invisible div over the entire page) but this issue wasn't present in Chrome or Safari. That appears to have been fixed. Examples are hard to provide since they almost always get fixed but in the moment its enough pain to always get me to drop Firefox.
If it always getting fixed shortly after, it probably means something is going on in your settings or in the background that is interfering at the time you are trying to access them. Just my two cents. I know when I run proton vpn, little snitch, my various extensions, etc. one of them is always the culprit no matter what browser I use.
If it gets fixed quickly, it was probably an issue with the particular website or a plugin of yours rather than Firefox's issue. People are fast to "conclude" it must be Firefox. You should also test in a private tab with no plugins enabled. That might very well also fix the issue.
