If you have multiple new post notifications from a watched topic they are collapsed into one notification. But the notification takes you to the last post instead of first one.
I will also note that if you have a new post notification that did not get retrieved in the notifications load, it will not be included for consideration in the collapsing, and thus even with proper collapsing you might not get sent to the correct location...
Now that I looked into it, that's exactly what's happening, if there is only a few new post notifications it sends you to the first one, but if there are more than what's loaded then it will point at the first one in the loaded batch.