diff --git a/core/modules/locale/src/LocaleConfigManager.php b/core/modules/locale/src/LocaleConfigManager.php
--- a/core/modules/locale/src/LocaleConfigManager.php	(revision 4be9fceb6b3b4cf0d54ac70efe80b6ac3f1d929e)
+++ b/core/modules/locale/src/LocaleConfigManager.php	(revision 8671e0d424fed96d50aacad941ad22a719b7f404)
@@ -528,6 +528,13 @@
    *   TRUE if interface translation is supported.
    */
   public function isSupported($name) {
+    // Disable the sync between the locale storage and configs / config
+    // overrides, so that we stop loosing translations when some module with
+    // shipped configs is enabled. That's a temporary fix to the issue. It seems
+    // to only affect websites with non-English language set as default.
+    // See https://www.drupal.org/project/drupal/issues/2806009 for details.
+    return FALSE;
+
     return $this->getDefaultConfigLangcode($name) == 'en' && $this->configStorage->read($name);
   }