try replace select by switcher

app/UI/VmCreate/Sections/AdditionalDiskSection.php

@@ -64,7 +64,7 @@ class AdditionalDiskSection extends BaseSection implements ClientArea
         //backup
         if ($this->configuration()->isPermissionAdditionalDiskBackup())
         {
-            $field = new Select('additionalDiskBackup');
+            $field = new Switcher('additionalDiskBackup');
             $field->setAvailableValues([
                 'on' => 'Enable',
                 'off'=>'Disable',