Neu JTL-Shop 5, seit heute Error 500

[neodg]

Ohne jegliche Änderung seit Wochen habe ich seit heute einen Error 500 beim Aufruf des Shops. In den Logs ist das hier zu finden:

[Tue Jan 12 18:00:58.991624 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: PHP Fatal error:  Uncaught TypeError: Return value of JTL\\Plugin\\PluginLoader::loadFromCache() must implement interface JTL\\Plugin\\PluginInterface or be null, string returned in /var/www/vhosts/domain.com/httpdocs/includes/src/Plugin/PluginLoader.php:60
[Tue Jan 12 18:00:58.991648 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: Stack trace:
[Tue Jan 12 18:00:58.991652 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #0 /var/www/vhosts/domain.com/httpdocs/includes/src/Plugin/PluginLoader.php(41): JTL\\Plugin\\PluginLoader->loadFromCache()
[Tue Jan 12 18:00:58.991655 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #1 /var/www/vhosts/domain.com/httpdocs/includes/src/Plugin/Helper.php(450): JTL\\Plugin\\PluginLoader->init()
[Tue Jan 12 18:00:58.991657 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #2 /var/www/vhosts/domain.com/httpdocs/includes/src/Shop.php(898): JTL\\Plugin\\Helper::bootstrap()
[Tue Jan 12 18:00:58.991660 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #3 /var/www/vhosts/domain.com/httpdocs/includes/globalinclude.php(130): JTL\\Shop::bootstrap()
[Tue Jan 12 18:00:58.991662 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #4 /var/www/vhosts/domain.com/httpdocs/index.php(6): require('/var/www/vhosts...')
[Tue Jan 12 18:00:58.991665 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr: #5 {main}
[Tue Jan 12 18:00:58.991667 2021] [fcgid:warn] [pid 5642] [client 1.2.3.4:42462] mod_fcgid: stderr:   thrown in /var/www/vhosts/domain.com/httpdocs/includes/src/Plugin/PluginLoader.php on line 60

Aber so wirklich schlau werde ich daraus leider nicht...