If a file's content is changed outside of ST2, and ST2 does its silent reload (or even the non-silent reload in case of any edits) the buffer updates to the new content. But the scroll-ability is not updated properly.
Say a file was only a few lines long, and then got refreshed and went off the visible area (thus meaning it should scroll). The 'mousehweel' up/down commands don't do anything. The page will scroll if you drag outside of the window and I even the minimap works, but mouse scrolling doesn't work.
Additionally to this, if the content grows horizontally rather than vertically then even minimap scrolling doesn't fix it, as the minimap doesn't scroll horizontally.
I've recently switched to OSX so I have only noticed it on OSX - it may also affect Win/Linux but I don't have an easy route to test it so haven't done so. (Sorry.)
I know it sounds like something of an edge case but for some reason I've been noticing it a lot lately, so it's obviously something that happens to me quite a bit for whatever reason. It probably doesn't help that I'm doing a lot of network share work, and if I boot up ST2 before mounting the share I get blank documents on session load which then refresh once I mount the volume. But that's not the only situation in which I get this behaviour.