Alex Pott
--- a/core/lib/Drupal/Core/Database/Connection.php
+++ b/core/lib/Drupal/Core/Database/Connection.php
   */
  public function __destruct() {
+    // Ensure all still-open transactions get auto-committed. Usually, this
+    // happens when the Transaction::__destruct() method is invoked, but during
+    // shutdown the object transaction order is unreliable. If the connection
+    // is destroyed first, we need to make sure to auto-commit all still-open
+    // transactions.
+    // Also see https://www.drupal.org/project/drupal/issues/1608374.
+    if ($this->isTransactionManagerStackActive) {
+      $this->commitTransactionOnDestruct();
+    }
+    else {
+      foreach (array_reverse($this->transactionLayers) as $name => $active) {
+        $this->popTransaction($name);
+      }
+    }
-    else {
-      foreach (array_reverse($this->transactionLayers) as $name => $active) {
-        $this->popTransaction($name);
-      }
-    }
+    // Ensure the deprecation layer does not have any transactions.
+    foreach (array_reverse($this->transactionLayers) as $name => $active) {
+      $this->popTransaction($name);
+    }
--- a/core/lib/Drupal/Core/Database/Connection.php
+++ b/core/lib/Drupal/Core/Database/Connection.php
   * Ensures that the client connection can be garbage collected.
   */
  public function __destruct() {
+    // Ensure all still-open transactions get auto-committed. Usually, this
+    // happens when the Transaction::__destruct() method is invoked, but during
+    // shutdown the object transaction order is unreliable. If the connection
+    // is destroyed first, we need to make sure to auto-commit all still-open
+    // transactions.
+    // Also see https://www.drupal.org/project/drupal/issues/1608374.
+    if ($this->isTransactionManagerStackActive) {
+      $this->commitTransactionOnDestruct();
+    }
+    else {
+      foreach (array_reverse($this->transactionLayers) as $name => $active) {
--- a/core/lib/Drupal/Core/Database/Connection.php
+++ b/core/lib/Drupal/Core/Database/Connection.php
    }
  }

+  /**
+   * Commit on destruction if a client transaction is still active.
+   *
+   * This method should only be called by __destruct().
+   *
+   * @internal
+   */
+  protected function commitTransactionOnDestruct(): void {
+    $this->connection->commit();