Nothing horrifying, but a few frustrations: 

Some accounts that I follow suddenly disappear from my feed and it turns out I'm not following them anymore. I wish I knew how that happened or at least had a way to track it.

I often can't see replies to posts. At first I assumed that it was because of accounts that I've muted, but I've only muted 2 and this happens a lot. Then today I did a search for a post and I saw the answer show up in my search, but I can't see it in the thread.