These steps might help to determine if an issue is related to your
setup/configuration or if the problem is a bug in Vimwiki.
dev branch.
cd $HOME
mkdir vw_tmp
cd vw_tmp
git clone -b dev --single-branch https://github.com/vimwiki/vimwiki.git
vimrc (you should still be in $HOME/vw_tmp)
vim min_vimrc
set nocompatible
filetype plugin on
syntax on
set runtimepath+=~/vw_tmp/vimwiki
let wiki = {}
let wiki.path = '~/vw_tmp/wiki'
let wiki.path_html = '~/vw_tmp/wiki/html'
let wiki.syntax = 'default'
let wiki.ext = '.wiki'
let g:vimwiki_list = [wiki]
min_vimrc
vim -u min_vimrc
\ww) and verify the issue still occurs.