[O] Struggling with setting up ox-koma-letter.el

[N. Jackson]

I am trying to get ox-koma-letter.el working in my Emacs (25.0.95).

I have been following the instructions at
http://orgmode.org/worg/exporters/koma-letter-export.html and I am
testing with the "A simple letter example"
(http://orgmode.org/cgit.cgi/worg.git/plain/exporters/koma-letter-new-example.org).

My org and my ox-koma-letter.el are from the Org Elpa org-plus-contrib
package (version 20160620) and are located in
~/.emacs.d/elpa/org-plus-contrib-20160620/.

I get an error message when I try to export the example letter using
`C-c C-e k p'. The message is

    org-export-as: Wrong number of arguments: #[(templates)
    "ŠebˆÆ^XÇÈÆÉ#…\\^@Ê ^YË !Ì=ƒX^@Í \"^[ÎÏ \"‰^\ ÎÐ
    \"E‰^]ƒ<^@ÑÒÎÓ \"\"ˆ‚W^@ƒW^@^MB^PÎÔ
    \"bˆÕÆxˆ`|ˆŠcˆ)+)‚^F^@*‡" [record object
    templates value begin signature nil re-search-forward "{{{[-A-Za-z0-9_]"
    t ...] 6 ("/data/projects/vc/emacs/emacs-25.0.95/lisp/org/org-macro.elc"
    . 3784)], 3

I can't read this error message due to all the escaped characters, but I
do see a mention of an incorrect file. The org-macro.elc file mentioned
in the error message is the one built in to Emacs and it should be
hidden.

I have normal-looking load path shadows, with the the elpa version
hiding the version built in to Emacs (e.g. list-load-path-shadows shows
for example that ~/.emacs.d/elpa/org-plus-contrib-20160620/org-macro
hides /data/projects/vc/emacs/emacs-25.0.95/lisp/org/org-macro).

I would welcome any help with getting this working.

Thanks,
N.