SOLUTION!
REMOVED:
add_filter( 'bbp_get_reply_content', array( $this, "shortcode_whitelist" ) );
FROM PLUGIN:
bbPress Advanced Statistics, file: class-bbpress-advanced-statistics-extras.php
CAUSE:
Breaks the loading of shortcodes.
I’m hopeful this will help someone else. It seemed to be a problem with the bbPress Advanced Statistics plugin.
UPDATE 3:
return apply_filters( 'bbp_get_reply_content', $content, $reply_id );
in bbpress/includes/replies/template.php
This code breaks the entire shortcode loading function.
If I patch this to say return $content; it will start working.
Now to see why this happened..
It seems to me that this is the problematic code:
in content-single-topic.php
<?php if ( bbp_has_replies() ) : ?>
<?php bbp_get_template_part( 'pagination', 'replies' ); ?>
<?php bbp_get_template_part( 'loop', 'replies' ); ?>
<?php bbp_get_template_part( 'pagination', 'replies' ); ?>
<?php endif; ?>
If I remove this code block, all of the shortcodes start working.
UPDATE 1:
More specifically, this is the exact row that the problem appears at:
<?php bbp_get_template_part( 'loop', 'replies' ); ?>
UPDATE 2:
I followed the problem down to..
in file loop-single-reply.php
<?php bbp_reply_content(); ?>
If I remove this line, the shortcodes starts magically working.
