I can reproduce it.
Workaround is :set guioptions+=l, :set guioptions-=L, :set guioptions+=r
or :set guioptions-=R.
When splitting window vertically, Vim shows scrollbar. It causes window
resize. When resizing window, Vim try to keep window completely on
screen. And currently it is performed by comparing window position with
workarea (not entire screen). Therefore, Vim window always moves when
it is across the boundary the two monitors.
We are discussing this problem in vim_dev.
Yukihiro Nakadaira - yukihiro.nakada...@gmail.com