diff --git a/core/components/minishop3/src/Services/Order/OrderStatusService.php b/core/components/minishop3/src/Services/Order/OrderStatusService.php
index 5185b1df..3c1544f5 100644
--- a/core/components/minishop3/src/Services/Order/OrderStatusService.php
+++ b/core/components/minishop3/src/Services/Order/OrderStatusService.php
@@ -104,13 +104,9 @@ public function change(int $orderId, int $statusId, bool $skipNotifications = fa
         );
 
         if ($oldStatus) {
-            if ($oldStatus->get('final')) {
-                return $this->modx->lexicon('ms3_err_status_final');
-            }
-            if ($oldStatus->get('fixed')) {
-                if ($status->get('position') <= $oldStatus->get('position')) {
-                    return $this->modx->lexicon('ms3_err_status_fixed');
-                }
+            $transitionError = $this->validateStatusTransition($oldStatus, $status);
+            if ($transitionError !== null) {
+                return $transitionError;
             }
         }
 
@@ -143,6 +139,11 @@ public function change(int $orderId, int $statusId, bool $skipNotifications = fa
             if ($msOrder->get('status_id') == $statusId) {
                 return $this->modx->lexicon('ms3_err_status_same');
             }
+
+            $transitionError = $this->validateStatusTransition($oldStatus, $status);
+            if ($transitionError !== null) {
+                return $transitionError;
+            }
         }
 
         $msOrder->set('status_id', $statusId);
@@ -173,6 +174,28 @@ public function change(int $orderId, int $statusId, bool $skipNotifications = fa
         return true;
     }
 
+    /**
+     * Validate transition from old status to new (final/fixed rules).
+     */
+    protected function validateStatusTransition(
+        ?msOrderStatusModel $oldStatus,
+        msOrderStatusModel $newStatus
+    ): ?string {
+        if (!$oldStatus) {
+            return null;
+        }
+
+        if ($oldStatus->get('final')) {
+            return $this->modx->lexicon('ms3_err_status_final');
+        }
+
+        if ($oldStatus->get('fixed') && $newStatus->get('position') <= $oldStatus->get('position')) {
+            return $this->modx->lexicon('ms3_err_status_fixed');
+        }
+
+        return null;
+    }
+
     /**
      * Send notifications for status change
      *
diff --git a/core/components/minishop3/tests/OrderStatusFixedRevalidateTest.php b/core/components/minishop3/tests/OrderStatusFixedRevalidateTest.php
new file mode 100644
index 00000000..4b1a9c15
--- /dev/null
+++ b/core/components/minishop3/tests/OrderStatusFixedRevalidateTest.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * Guards fixed/final status re-validation after plugin mutation (issue #382).
+ *
+ * Run: php tests/OrderStatusFixedRevalidateTest.php
+ */
+
+declare(strict_types=1);
+
+$fail = static function (string $message): never {
+    fwrite(STDERR, "FAIL: {$message}\n");
+    exit(1);
+};
+
+$source = file_get_contents(dirname(__DIR__) . '/src/Services/Order/OrderStatusService.php');
+if ($source === false) {
+    $fail('cannot read OrderStatusService.php');
+}
+
+if (!str_contains($source, 'function validateStatusTransition')) {
+    $fail('OrderStatusService must define validateStatusTransition');
+}
+
+if (!preg_match('/function validateStatusTransition[\s\S]*ms3_err_status_fixed/s', $source)) {
+    $fail('validateStatusTransition must enforce fixed status position rule');
+}
+
+if (!preg_match(
+    '/\$resolvedStatusId\s*!==\s*\$statusId[\s\S]*validateStatusTransition\s*\(\s*\$oldStatus\s*,\s*\$status\s*\)/s',
+    $source
+)) {
+    $fail('OrderStatusService must re-run validateStatusTransition after plugin status mutation');
+}
+
+fwrite(STDOUT, "OK OrderStatusFixedRevalidateTest\n");
+exit(0);