Catching up by clicking "N new statuses" freezes timeline
I noticed that while scrolled down on an active timeline, after a while the notification would say 4567 new statuses or similar. Once I clicked that button (or scrolled to the top), the timeline froze while waiting to load all those new statuses and display them.
Instead of trying to load thousands of new statuses, when you statuses are loaded in bulk like that, and the number exceeds a certain number, say, 100-200, then it shouldn't try to load all of them. It could possibly reset the feed and load the top 25 or 100 or so.