I tried syncing my vertical and horizontal mouse sensitivity based on the current top-voted and accepted answer on the question: How can I sync vertical/horizontal mouse sensitivities?
The [Controls] section does not exist in my Skyrim.ini file so I added one at the end of the text file and added
fMouseHeadingXScale=0.0200 below it, as suggested by the aforementioned answer.
However, the game now makes vertical mouse movement very low (very slow and almost non-moving), and only responds properly to horizontal mouse movement. The mouse cursor vertical movement in the menu before you start the game and the in-game menus work fine, though.
I also tried putting the [Controls] section and the 'fMouseHeading' variables just below the [General] section (which is the first section), but the same thing happens. Removing the [Controls] section makes vertical mouse movement work fine again.
I have all the current DLCs installed, and all the unofficial patches for Skyrim and the DLCs installed.
Is there a fix for this? Or is the fix in the aforementioned answer now made obsolete by the official or unofficial patches?