BTW, I wasn't able to export manual.org using Org mode version 9.1.4
(9.1.4-elpaplus @ /Users/dk/.emacs.d/elpa/org-plus-contrib-20171205/).
It fails with this message:
format: Symbol’s value as variable is void: M-x
Does it depend on a more recent Org mode?
The file is in master branch. You need to use that to export it.