title: MS Office opens documents readonly with WebDAV
body: <p>We implemented our own WebDAV server. Some users having Office (Word, Excel) open documents read-only. On problem computers queries are next:</p>
  
  <ol>
  <li>OPTIONS <a href="http://pastie.org/10957339" rel="nofollow noreferrer">http://pastie.org/10957339</a>, response (after some chain of NTLM auth): <a href="http://pastie.org/10957337" rel="nofollow noreferrer">http://pastie.org/10957337</a> (equal to these ones, where problem not reproduces)</li>
  <li>GET</li>
  <li>HEAD</li>
  <li>HEAD</li>
  </ol>
  
  <p>Normal queries (on healthy computers) are: OPTIONS, HEAD, LOCK, GET... So, Word do not attempts to LOCK document, and opens it readonly.</p>
  
  <p><strong>We have already tried:</strong></p>
  
  <ol>
  <li>Checked WebDAV link, it is of<strong>e</strong> (as you can see in OPTIONS query)</li>
  <li>Checked, that OPTIONS response contains header MS-Author-Via: DAV</li>
  <li>Checked, that server does not crash. All responses are OK.</li>
  <li>Set registry key 
  <code>HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Common\Internet\OpenDocumentsReadWriteWhileBrowsing</code> to 1 as said <a href="https://social.technet.microsoft.com/Forums/office/en-US/06fedd90-4889-45ca-949d-60b76d74dd15/ms-word-open-document-readonly-with-webdav?forum=officeitproprevious" rel="nofollow noreferrer">here</a>.</li>
  <li>Set registry key <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters\BasicAuthLevel</code> to 2, and <code>HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Internet\BasicAuthLevel</code> to 2 as said <a href="https://support.microsoft.com/en-us/kb/2123563#mt4" rel="nofollow noreferrer">here</a>.</li>
  <li>Open documents from <a href="https://www.ajaxbrowser.com" rel="nofollow noreferrer">https://www.ajaxbrowser.com</a> - all OK, documents opens read-write.</li>
  <li>Clearing cookies in IE, logging in IE (to provide cookies for MS Word)</li>
  <li>Trying to find differences between problem computers and healthy ones. Problem reproducing on different versions of Office, different versions of Windows (7, 8, 10), all computers connected over proxy (healthy ones too).</li>
  <li>Сlear keys in <code>HKEY_CURRENT_USER\Software\Microsoft\Office\&lt;version&gt;\Common\Internet\Server Cache</code> as said <a href="https://www.webdavsystem.com/server/documentation/ms_office_read_only" rel="nofollow noreferrer">here</a>.</li>
  </ol>
  
  <p>Have any clue? Why is Office not trying to LOCK the document?</p>