dbus problem: "notifications-notify :on-action" stops working

[Peter Münster]

Hi,

Sometimes, the call-back function specified in ":on-action" of the
`notifications-notify' function is no more called and I have to restart
emacs to make it work again.

I was able (but not always) to reproduce this problem with this simple
test file:

--8<---------------cut here---------------start------------->8---
(require 'notifications)

(defun my-test-action (id ignore)
  (message "Success (id = %d)" id))

(defun my-test ()
  (interactive)
  (message "Begin test (id = %d)"
           (notifications-notify
            :title     "title"
            :timeout   30000
            :actions   '("key" "click here")
            :on-action 'my-test-action)))

(global-set-key [?\C-a] 'my-test)
(switch-to-buffer "*Messages*")
--8<---------------cut here---------------end--------------->8---

I save it in /tmp/init.el and start "emacs -Q -l /tmp/init.el". Then I
press about a dozen times "C-a" followed by a click on "click here".
Then I wait about 2-3 minutes and try it again: no more "Success".

Can others reproduce this behaviour?

Where could be the problem, and how could I debug it?

TIA for any help!
-- 
           Peter