Hi Peter, I should report to you a good news. Today I tried to install the newest Security Monthly Quality Rollup (KB4493472). Out of my expectation, the installation went through successfully without a single problem. While one cannot exclude the possibility that Microsoft did something unique with this rollup (you know better about it), the fixes in the past two weeks under your guidance certainly played an important role for the success. After installing the update, I ran SURT again, which returned exactly the same CheckSUR.log as before with 45 errors concerning missing deployment keys. Are these errors of a practical significance? Please let me know how to proceed from this point. Thank you very much.