FYI: @technocrati responded directly to my NGG bug report on this with the following suggestion...
"A quick look at the Random Content code has me thinking this is a due to a known issue in WordPress core with recursive filtering of the_content ... which appears to have been finally sorted out (after 4 years!) and should be committed to the WordPress 4.1 branch.
In the meantime, you can try adding the following to your wp-config.php file as a temporary work-around:
define( 'NGG_DISABLE_FILTER_THE_CONTENT', true );
Please note, it may cause unexpected issues elsewhere in NextGEN Gallery and its compatibility with various other plugins and themes."
So I tried this, with no luck. My reply...
"FYI: Adding this to wp-config did not resolve the issue.
Perhaps "recursive filtering of the_content" is not the cause after all?
If it is, and that is resolved in WP 4.1, I can certainly wait. But I am also happy to help troubleshoot further."