Spacemacs menu in mini-buffer displays Dired+ "C-x D A" command unreliably

Question

Two weeks ago I installed Dired+.

I successfully used Dired+ C-x D A (diredp-add-to-dired-buffer) command. But the Dired+ C-x D A command is not always available. Sometimes after C-x, the D appears in the Spacemacs menu, in the minibuffer, like this:

D -> +prefix

Other times D is missing from the Spacemacs menu. Although the Dired+ help displays as expected:

SPC SPC diredp-dired-plus-help

The inclusion of D in the menu seems random.

Also, when C-x D A is not available, it is not found in SPC h d k.

However, M-x diredp-add-to-dired-buffer works as expected.

I tried rebooting.

Like Drew said, maybe some other package I use might be grabbing the key binding. I haven't checked that yet.

Maybe I installed Dired+ the wrong way. My .spacemacs file contains dired+ twice:

(defun dotspacemacs/layers ()
  (setq-default
..
   dotspacemacs-additional-packages '(dired+)
)
..
(custom-set-variables
 '(package-selected-packages
   (quote
    (disaster dired+

What else could be causing the intermittent spacemacs-menu behavior?

I contacted the author of Dired+, but he doesn't know Spacemacs.

I am using Emacs 25.2.1 with Evil Spacemacs and Ivy on Linux.