functions.php is being included twice, creating PHP fatal errors
Ah, jeez: the ol’ check-all-your-plugins-first routine would’ve saved me some time. Apparently a 3rd-party ACF plugin, https://wordpress.org/plugins/acf-google-font-selector-field/, was the cause of the issue. The slow page loading I mentioned was also remedied. That’s too bad. I need that stupid plugin.