on Mon Nov 21 2016, Michael Albinus <michael.albinus-AT-gmx.de> wrote:

> Dave Abrahams <dave@boostpro.com> writes:
>
> Hi Dave,
>
>> More info.  Ido uses recentf, which has an interaction with TRAMP
>> documented here: https://www.emacswiki.org/emacs/RecentFiles#toc12
>
> Well, there are also other mysteries. In the git logfile, there is the
> entry
>
> commit b2b84b166a7ac454850ab4832ef40a41dce74cf7
> Author: Leo Liu <sdl.web@gmail.com>
> Date:   Fri Dec 25 19:10:13 2015 +0800
>
>     * ido.el (ido-add-virtual-buffers-to-list): Use bookmark-get-filename.
>
> Maybe it is related.
>
> Could you, pls, rerun your test like this:
>
> M-x tramp-cleanup-all-buffers
> M-: (setq tramp-verbose 10)
> C-x b
>
> It will fail like reported. But there will also be a Tramp debug buffer,
> containing a backtrace. This might tell us what triggers the new Tramp
> connection.

Voilà: