That’s has to do with the backend server that’ve been chosen at the preference page. Servers becomes unavailable all the time, and the frontend don’t change a server when it happens. Just choose a few servers that works well and you trust, and switch back and forth when needed.
I guess you’re talking about iOS, so yeah they had no choice, everything is Safari based there (for now). But on android, as I mentioned at my comment above, it’s chromium based.
Why’s that? I actually find all the desktop apps shows the Post’s imgs/gifs as a small thumbnail, which I don’t like when scrolling the feed. For me everything there works well and pretty convenient.