The error log you posted is the log from MODx. 500 errors aren’t log in this file.
The location of the PHP error log depends on your server configuration. See the post below for more information.
As you use Imagick to create the thumbnails, it could also be helpful to know the version of Imagick on your system. Check phpinfo() for the information.
I highly doubt the version of Adobe InDesign has anything to do with this problem.