500 error

A few months ago (not sure exactly when), I started getting a fatal error any time I click on a portfolio item. I have tried disabling all plugins, but the problem still persists. I am on 6.5.3, running Genesis/Monochrome Pro 1.5.0, version 3.3.8 of the portfolio plugin, and PHP 8.2. I believe this is the error it’s throwing:

PHP Fatal error: Uncaught Error: Undefined constant “\xe2\x80\x98genesis_loop\xe2\x80\x99” in /nas/content/live/XXXX/wp-content/themes/monochrome-pro/single-portfolio.php:11\nStack trace:\n#0 /nas/content/live/XXXX/wp-includes/template-loader.php(106): include()\n#1 /nas/content/live/XXXX/wp-blog-header.php(19): require_once(‘/nas/content/li…’)\n#2 /nas/content/live/XXXX/index.php(17): require(‘/nas/content/li…’)\n#3 {main}\n thrown in /nas/content/live/XXXX/wp-content/themes/monochrome-pro/single-portfolio.php on line 11, referer: https://XXXX.wpengine.com/press-media/

Any ideas to help me debug this will be appreciated. I have not changed anything on my site in years (other than updating WP, PHP, and existing plugins).

Thanks.