I have several sites that are doing this and also a handful that are working correctly.
The default "Home" title tag set in the Settings menu appears in all the sub pages of the site, regardless of the titles that are set on the individual page's All In One settings.
There's no Cache plugin installed. I've tried swapping out the <title> section of one of the working pages with one of the non-working. <?php wp_head(); ?> is installed.
It's only the page title... descrtiptions and keywords are working fine.
All WP and plugin installs have been updated.