Firefox’s Enhanced Tracking Protection (Strict Mode) is known to cause issues on x.com
There were no “issues”; everything was working completely fine. This is a deliberate decision to force people to turn off tracking protection.
I saw a recommendation to use Firefox’s container extension https://support.mozilla.org/en-US/kb/containers, but it’s disabled in private browsing windows, and I always use private browsing windows.
I don’t but many people do since many creators use Twitter for that. I personally don’t get why they don’t switch to Mastodon or another Fediverse software since there are probably NSFW instances too and if not some of them could team up and create one.