Strange behavior editing a file from Dired

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

When I review mails before sending them out, I move down through
a Dired buffer typing C-o.  Sometimes I switch to the other window
and type C-x 1, edit that message file, and save it.  Then I switch
back to the Dired buffer.

Occasionally I find that point has moved up some number of lines in
the Dired buffer.  The number of lines varies.

This has been happening for months.

When I notice it, I type C-h l, but I have not noticed anything
significant in the output.  And I have not been able to reproduce it.

Has anyone else seen something like this?

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.