Those images match the signature of a central directory.
unzip -t 01-0557-3.jpg
warning [01-0557-3.jpg]: zipfile claims to be last disk of a multi-part archive; attempting to process anyway, assuming all parts have been concatenated together in order. Expect "errors" and warnings...true multi-part support doesn't exist yet (coming soon). error [01-0557-3.jpg]: missing 1852006951 bytes in zipfile (attempting to process anyway) error [01-0557-3.jpg]: attempt to seek before beginning of zipfile (please check that you have transferred or created the zipfile in the appropriate BINARY mode and that you have compiled UnZip properly)
unzip -t 05-0995-2.jpg
warning [05-0995-2.jpg]: zipfile claims to be last disk of a multi-part archive; attempting to process anyway, assuming all parts have been concatenated together in order. Expect "errors" and warnings...true multi-part support doesn't exist yet (coming soon). error [05-0995-2.jpg]: missing 1689894850 bytes in zipfile (attempting to process anyway) error [05-0995-2.jpg]: attempt to seek before beginning of zipfile (please check that you have transferred or created the zipfile in the appropriate BINARY mode and that you have compiled UnZip properly)
Whereas with a normal file: unzip -t 01-0557-2.jpg
Archive: 01-0557-2.jpg End-of-central-directory signature not found. Either this file is not a zipfile, (...)
01-0557-3.jpg contains "50 4B 05 06" at offset 0x4E24B and 05-0995-2.jpg at 0x309DE. Since they're just 4 bytes at an arbitrary offset amongst "random" data, it's apparently a statistical false positive. In fact, the more throughly ZipDirectoryReader detects it as 'zip-bad', 'trailing bytes after the end of the file comment'. Maybe we should strength the checks at MimeMagic.php
What were you changing in the db? I don't get that "magic change back" that you report. Perhaps it was metadata update was triggering it.
Setting these values you should be safe:
img_name img_size img_width img_height img_metadata img_bits img_media_type img_major_mime img_minor_mime img_sha1 01-0557-3.jpg 377382 599 800 a:1:{s:22:"MEDIAWIKI_EXIF_VERSION";i:2;} 8 BITMAP image jpeg 1fyq01rqsw47yhvl4sqg66gr4d60j0f 05-0995-2.jpg 220187 800 565 a:1:{s:22:"MEDIAWIKI_EXIF_VERSION";i:2;} 8 BITMAP image jpeg ghuv3z91zq81vub5v8zj9tmjziojzrh