I have been using a handy plugin called Debug Bar and Debug Media (an addon to Debug Bar) that can help with reporting the settings on a WordPress installation. By default there are many PHP, image processing, and server settings that are set behind the scenes to a default. Modifying these can be a last resort to a memory issue, or some sort incompatibility.
I have recently come across a bug from v4.5 to the current version that prevents large images (3500px+ across for example) from uploading successfully. The image uploads but the thumbnail progress fails with an HTTP error. This plugin helps me analyze various settings to see if there are consistencies around the image library being used. When reporting an issue providing these can help a lot.
Debug Bar - master debug bar plugin
Debug Media - addon to report Media Library image processing settings
Here's some example output:
<servername>.secureserver.net
PHP
5.6.27
MySQL
5.6.32
Memory Usage
28,173,720 bytes
Media Debugging Info
Active Editor WP_Image_Editor_GD
Imagick Module Number 1620
ImageMagick Version ImageMagick 6.5.4-7 2014-02-10 Q16 OpenMP http://www.imagemagick.org
GD Version bundled (2.1.0 compatible)
Ghostscript Version 8.70
Memory Limit 256M
Max Execution Time 60
Max Input Time 60
Upload Max Filesize 256M
Post Max Size 65M
