I can reproduce this if I have something like the following in the preamble:

#+COLUMNS: %45ITEM %10BEAMER_ENV(Env) %10BEAMER_ACT(Act) %4BEAMER_COL(Col)
%8BEAMER_OPT(Opt)

org-set-property seems to be extracting these settings for use as heading
properties. Removing this line also removes the properties when using C-c
C-x p.

On 28 September 2017 at 08:16, Nicolas Goaziou <mail@nicolasgoaziou.fr>
wrote:

> Hello,
>
> James Harkins <jamshark70@zoho.com> writes:
>
> > On September 27, 2017 14:03:06 Eric S Fraga <esflists@gmail.com> wrote:
> >
> >> On Wednesday, 27 Sep 2017 at 11:53, James Harkins wrote:
> >>> Hi,
> >>>
> >>> There seems to be a mistake in the org-mode Ubuntu 16.02 packages.
> >>>
> >>> For beamer, if I C-c C-x p to add a property, one of the predefined
> options is:
> >>>
> >>>      :BEAMER_act(Act): 1
> >>
> >> I think (could be wrong on this) that org includes any properties you
> >> already have as pre-defined options available to you.  Maybe you have
> >> this property already in your file?
> >
> > No, I have never used this (incorrect) property. This occurs in
> > a brand new org file too.
> >
> > Oh, just did a search: ox-beamer.el, line 81, defines columns for
> > beamer properties, including the incantation "%10BEAMER_act(Act)" --
> > which, except for the %10, matches the behavior precisely. It appears
> > that C-c C-x p is treating this as the true name of the property, when
> > it's really something for display.
> >
> > Anyway, the string inserted by C-c C-x p just doesn't work.
>
> FWIW, I cannot reproduce it.
>
> Regards,
>
> --
> Nicolas Goaziou
>
>