Permalink 404 error with /%year%/%monthnum%/%postname%/ as default

I am using the YD Network-wide options plugin and have set my “Master” site permalinks to use the /%year%/%monthnum%/%postname%/ structure.

My “slave” sites inherit the permalink setting, but when I click the first default post, I receive a 404 error. If I go into the permalink settings of the “slave” site and simply click the “Save changes” button (with /%year%/%monthnum%/%postname%/ already selected), the 404 error issue goes away.

If I set my master to use this permalink structure: /%year%/%monthnum%/%day%/%postname%/ I don’t get the 404 error.

I don’t want my users to have to mess with permalink settings, and I’d rather not include /%day%/ in the URL.

Other posts related to this issue lead me to believe this may be an .htaccess issue, so here is my code for that:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

You can view this issue live at the following site: http://flashdraft.org/lorem/

Click the link called “Sample Assignment”

Thanks for your help!