Undefined index: siteSettings when updating entry types I'm receiving an Undefined index: siteSettings when trying to save changes to entry types (both new and existing). Of course, this is only occurring on a production server - local server with up-to-date copies of the DB is working as expected. Also, we're not using project config.

yii\base\ErrorException: Undefined index: siteSettings in /chroot/home/sitename/vendor/craftcms/cms/src/services/Sections.php:608
Stack trace:
#0 /chroot/home/sitename/vendor/craftcms/cms/src/web/ErrorHandler.php(80): yii\base\ErrorHandler-&gt;handleError(8, 'Undefined index...', '/chroot/home/ly...', 608)
#1 /chroot/home/sitename/vendor/craftcms/cms/src/services/Sections.php(608): craft\web\ErrorHandler-&gt;handleError(8, 'Undefined index...', '/chroot/home/ly...', 608, Array)
#2 /chroot/home/sitename/vendor/craftcms/cms/src/services/ProjectConfig.php(872): craft\services\Sections-&gt;handleChangedSection(Object(craft\events\ConfigEvent))
#3 [internal function]: craft\services\ProjectConfig-&gt;craft\services\{closure}(Object(craft\events\ConfigEvent))
#4 /chroot/home/sitename/vendor/yiisoft/yii2/base/Component.php(627): call_user_func(Object(Closure), Object(craft\events\ConfigEvent))
#5 /chroot/home/sitename/vendor/craftcms/cms/src/services/ProjectConfig.php(551): yii\base\Component-&gt;trigger('addItem', Object(craft\events\ConfigEvent))
#6 /chroot/home/sitename/vendor/craftcms/cms/src/services/ProjectConfig.php(866): craft\services\ProjectConfig-&gt;processConfigChanges('sections.0ad0be...')
#7 [internal function]: craft\services\ProjectConfig-&gt;craft\services\{closure}(Object(craft\events\ConfigEvent))
#8 /chroot/home/sitename/vendor/yiisoft/yii2/base/Component.php(627): call_user_func(Object(Closure), Object(craft\events\ConfigEvent))
#9 /chroot/home/sitename/vendor/craftcms/cms/src/services/ProjectConfig.php(551): yii\base\Component-&gt;trigger('addItem', Object(craft\events\ConfigEvent))
#10 /chroot/home/sitename/vendor/craftcms/cms/src/services/ProjectConfig.php(395): craft\services\ProjectConfig-&gt;processConfigChanges('sections.0ad0be...', true)
#11 /chroot/home/sitename/vendor/craftcms/cms/src/services/Sections.php(1174): craft\services\ProjectConfig-&gt;set('sections.0ad0be...', Array)
#12 /chroot/home/sitename/vendor/craftcms/cms/src/controllers/SectionsController.php(374): craft\services\Sections-&gt;saveEntryType(Object(craft\models\EntryType))
#13 [internal function]: craft\controllers\SectionsController-&gt;actionSaveEntryType()
#14 /chroot/home/sitename/vendor/yiisoft/yii2/base/InlineAction.php(57): call_user_func_array(Array, Array)
#15 /chroot/home/sitename/vendor/yiisoft/yii2/base/Controller.php(157): yii\base\InlineAction-&gt;runWithParams(Array)
#16 /chroot/home/sitename/vendor/craftcms/cms/src/web/Controller.php(187): yii\base\Controller-&gt;runAction('save-entry-type', Array)
#17 /chroot/home/sitename/vendor/yiisoft/yii2/base/Module.php(528): craft\web\Controller-&gt;runAction('save-entry-type', Array)
#18 /chroot/home/sitename/vendor/craftcms/cms/src/web/Application.php(299): yii\base\Module-&gt;runAction('sections/save-e...', Array)
#19 /chroot/home/sitename/vendor/craftcms/cms/src/web/Application.php(565): craft\web\Application-&gt;runAction('sections/save-e...', Array)
#20 /chroot/home/sitename/vendor/craftcms/cms/src/web/Application.php(278): craft\web\Application-&gt;_processActionRequest(Object(craft\web\Request))
#21 /chroot/home/sitename/vendor/yiisoft/yii2/base/Application.php(386): craft\web\Application-&gt;handleRequest(Object(craft\web\Request))
#22 /chroot/home/sitename/html/index.php(23): yii\base\Application-&gt;run()
#23 {main}


Application Info

PHP version: 7.1.33
OS version: Linux 2.6.32-754.18.2.el6.x86_64
Database driver &amp; version: MySQL 5.6.43
Image driver &amp; version: Imagick 3.4.3RC1 (ImageMagick 6.7.2-7)
Craft edition &amp; version: Craft Pro 3.3.19
Yii version: 2.0.31
Twig version: 2.12.3
Guzzle version: 6.5.1
Imagine version: 1.2.3-dev
Even with 'useProjectConfigFile' =&gt; false, it is still active under the hood.

Could you run ./craft project-config/rebuild and see if that fixes the issue?