I’ve solved it today after ages.
So there is a Problem with a Windows Update…again…which updated maybe utilities or parts of the Windows Webserver IIS.
My web.config did eliminate my python background process because it did not find a server to run manage.py because of the rewrite configuration.
If anyone is interested here is my new config:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<location path="" overrideMode="Deny">
</location>
<system.webServer>
<rewrite>
<rules>
<clear />
<rule name="Redirect to HTTPS" enabled="true" stopProcessing="true">
<match url="(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false">
<add input="{HTTPS}" pattern="^OFF$" />
</conditions>
<action type="Redirect" url="https://{HTTP_HOST}/{R:1}" redirectType="Permanent" />
</rule>
<rule name="seafilehttp" stopProcessing="true">
<match url="seafhttp/(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
<action type="Rewrite" url="http://127.0.0.1:8082/{R:1}" appendQueryString="true" logRewrittenUrl="true" />
</rule>
<rule name="seafile" enabled="true" stopProcessing="true">
<match url="(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
<action type="Rewrite" url="http://localhost:8080/{R:1}" appendQueryString="true" logRewrittenUrl="true" />
</rule>
</rules>
<outboundRules>
<preConditions>
<preCondition name="ResponseIsHtml1">
<add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html" />
</preCondition>
</preConditions>
</outboundRules>
</rewrite>
<httpErrors errorMode="DetailedLocalOnly" />
<security>
<requestFiltering allowDoubleEscaping="true">
<requestLimits maxAllowedContentLength="4294967295" />
</requestFiltering>
</security>
</system.webServer>
</configuration>