Seeking understanding Bit Rot in Aperture

[sgbotsford]

ImageMagick 6.9.6-6 Q16 x86_64 2016-12-09
Mac: 2012 Mac Pro, 24 GB ram 3.2 GHz 4 core, Yosemite.
Aperture 3.6

Shared files: https://drive.google.com/open?id=0B7a-6 ... U1yNlhVTUU
Screenshot.png Illustration of the issue. Screenshot is from Aperture, showing an intact preview, but corrupted image.

Copying the image from the library gives us the second file there Bad.jpg

Nik, Photoshop and preview all found the same half image.
Reimporting the image into aperture gave me a second copy with the fault. This is not an oddball library issue.

Next step:
I used

convert -flop Bad.jpg Test.jpg

This file opens normally, but is slightly smaller.

convert -flop Test.jpg Test2.jpg

Reflips it.

compare Bad.jpg Test2.jpg diff.png

gives me a red shadow image, with no obvious artifact.

So questions:

A: What just happened? What kind of error affects the reading of this file in 4 out of 5 image packages. (Yes, it's Magic. <rueful grin>)

B: What is the best technique to minimize data loss in terms of opening and writing out? So far the simplest command I've found is

convert old.jpg new.jpg

But this results in a file that is roughly 100K smaller

C: What caused this in the first place? I found this one shortly after I wrote keywords back to files.

D: Is there a clever IM script that can detect these?

The image itself is trash. I keep it more to have a visual crop history than for any photographic virtue.

[snibgo]

With v6.9.5-3 on Windows 8.1, the file bad.jpg converts with no problem, and views in Microsoft Photo Viewer with no problem. But the file may have a problem that v6.9.5-3 ignores.

It contains a thumbnail, so if a program has problems with the main image, the thumbnail may display okay.