This is really odd. Here's the key mapping from my .vimrc:
noremap <C-n> :vert new<CR>
The expected behaviour when I press CTRL-n is that it opens a vertical window but it somehow opens a horizontal window on top of the current.
The problem only arises for the mappings. When I try
:vert new from Vim, I get what I want, a new vertical window.
I have also tried
:vsplit new, they all work fine when I manually initiate them. Does not work with CTRL-n.