I've seen this issue a couple of times on different sites

I've seen this issue a couple of times on different sites now. To resolve the 500 error, I have to completely remove the Defender Plugin.

Fatal error: Cannot use object of type WP_Error as array in /var/www/share/vhost-www-remc13-org/wp-content/plugins/wp-defender/app/module/scan-module/model/class-wd-scan-result-core-item-model.php on line 275