IIS 8 does not recognized web.config

I have run multiple PHP (Laravel) applications on my IIS 8 (Win 2012) Server. This is the web.config file for all of my apps:

<configuration>
  <system.webServer>
    <rewrite>
      <rules>
        <rule name="Imported Rule 1" stopProcessing="true">
          <match url="^(.*)/$" ignoreCase="false" />
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
          </conditions>
          <action type="Redirect" redirectType="Permanent" url="{R:1}" />
        </rule>
        <rule name="Imported Rule 2" stopProcessing="true">
          <match url="^" ignoreCase="false" />
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
            <add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />
          </conditions>
          <action type="Rewrite" url="index.php" />
        </rule>
      </rules>
    </rewrite>
  </system.webServer>
</configuration>

But on one appliation, IIS make from time to time a problem: My app don't work, because the URLs are wrong. If i restart the Webserver OR change the web.config file (add a empty space or something...), it works again.

I have no idea...my other apps works without problems, and it's the same web.config code.

All Users (IIS_IUSR, Admins, etc) have full write and read access.

My apps are structured in folders, see here:

And i call it with 10.0.0.7/doku or 10.0.0.7/lagerverwaltung.