Can't pan map far enough south

For some reason I can't pan the in-game map far enough south-east (past Riften). Basically I point my mouse at the bottom right of the screen and the map barely scrolls to Riften, it just wont go further.

I don't know how long it's been present but have only noticed it since I got the Dawnguard expansion (where I frequently try to fast travel to Fort Dawnguard). So it might be an issue in the base game too.

I can't find anyone else online mentioning it but I'd like to know if you guys know a fix. What I've been doing thus far is just fast travelling to a closer town, then immediately fast travelling from there (I am yet to experience the problem happening twice in a row).

It isn't a distance thing because I've traveled from the Fort to Castle Volkihar, it seems to be random, and only affects that south east corner of the map.

By Default, the Skyrim map can be a little touchy when it comes to fast-traveling to the new Dawnguard locations.

The only reliable solution I've found is to rotate the map (by right-click dragging), which changes the angle and pushes the locations "up", making them much easier to select.

The way I've usually gotten the map to cooperate has been to Fast Travel in two hops; the map seems more willing to pan to the extreme edges if you're closer to them, so I find it easier to get it to pan over the Dawnguard Fort if I'm in or near Riften, and likewise easier to get to the areas that the Dawnguard DLC added in the North-west by if I'm in or near Solitude.

The "map" is actually an extreme camera pan of a very-highly LOD'd gameworld. Like any other camera in the game, you can tweak the INI to change the view.

Improved 3D World Map on the Skyrim Nexus is actually a collection of INI tweaks that improves the functionality of the map greatly, including letting you see the southernmost settlements, with a DIY guide as its primary download.