Hello, thanks for your reply.

On Thu, Dec 17, 2015 at 6:03 PM Nicolas Goaziou <mail@nicolasgoaziou.fr> wrote:
Since cd439bc5138fc22a4f2532f90c87629c1deec3e3 (committed 2 years ago),
`org-element-set-element' can handle strings fine.

Yes, you are right. I got confused by the indentation.
 
Also, I cannot reproduce your problem in current stable release of Org.
You may want to update it.

It's a clean Spacemacs installation, it get's fresh Org from ELPA and compiles it. I found out that removing the *.elc files helps... weird. It might be a Spacemacs-related issue or a general Emacs issue but looks like Org-mode is fine :)

Thanks for your help!

Regards, Ilya.