Problem
Browsing the vrchat.com/home website can end up in favorite worlds endpoint blocking you out because of too many requests (screenshots #1 #2 #3). This results in favlists dropdowns and fav/unfaving button not working properly (screenshots #4 and #5). This happens to me every time when I try to unfav a world or two to fav a new one.
How to reproduce
[User perspective:]
In general it happens for me all the time when I open up the website to fav a world, but often I find my world favlists to be full, so I open favs to look for worlds to unfav, then try to fav the new world.
[Tech perspective:]
You can also just open a world view page, then refresh a couple of times, and you'll see that there's a bunch of https://vrchat.com/api/1/favorites?n=XXX&offset=XXX&type=world happening and often the last few of them failing due to 429 Too Many Requests. Especially if you fav or unfav a world, because that single action also makes ~19 requests for the world favlist(!!!) and it's easy to combo with the similar ~19 requests happening right after loading the page.
I believe the endpoint might have too restrictive request limits, seeing how similar spams of e.g. friend list endpoint are just fine.