system.webServer/httpCompression settings don't apply after the first tune

[NemoDima]

system.webServer/httpCompression settings don't apply after the first tune.
I want to change the dynamic compression level, but the new setting doesn't influence the final size of the transferred data.

Environment:
WinOS 2016 ver1607
IIS 10.0.14393.0
additionally installed https://download.microsoft.com/download/6/1/C/61CC0718-ED0E-4351-BC54-46495EBF5CC3/iiscompression_amd64.msi

I have added site, downloaded mentioned msi-package, enabled static and dynamic compression, setting up the level of compression, added types (application/json and application/json; charset=utf-8), add URLrewrite rule for the brotli.

After this action, brotli compression applying for the site successfully, but if I want to change or disable the compression it doesn't work. It looks like system.webServer/httpCompression doesn't work at all. I noticed that web.config changed but settings don't influence it all.

Only compression section works and provides the ability to disable compression

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <!-- To customize the asp.net core module uncomment and edit the following section. 
  For more info see https://go.microsoft.com/fwlink/?linkid=838655 -->
  <system.webServer>
    <modules>
      <remove name="WebDAVModule" />
    </modules>
    <handlers>
      <remove name="WebDAV" />
      <remove name="aspNetCore" />
      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
    </handlers>
    <aspNetCore processPath="dotnet" arguments=".\GoodStreamWebSpa_BigClients.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" requestTimeout="01:00:00" />
        <httpCompression>
            <remove name="gzip" />
            <remove name="br" />
            <scheme name="br" doDynamicCompression="true" dll="%ProgramFiles%\IIS\IIS Compression\iisbrotli.dll" dynamicCompressionLevel="2" />
            <scheme name="gzip" doStaticCompression="true" doDynamicCompression="true" dll="%ProgramFiles%\IIS\IIS Compression\iiszlib.dll" dynamicCompressionLevel="9" />
            <dynamicTypes>
                <add mimeType="application/json" enabled="true" />
                <add mimeType="application/json; charset=utf-8" enabled="true" />
            </dynamicTypes>
            <staticTypes>
                <add mimeType="application/json" enabled="true" />
                <add mimeType="application/json; charset=utf-8" enabled="true" />
            </staticTypes>
        </httpCompression>
        <rewrite>
            <rules>
                <rule name="Prioritize Brotli">
                    <match url="(.*)" />
                    <conditions>
                        <add input="{HTTP_ACCEPT_ENCODING}" pattern="\bbr(?!;q=0)\b" />
                    </conditions>
                    <serverVariables>
                        <set name="HTTP_ACCEPT_ENCODING" value="br" />
                    </serverVariables>
                    <action type="None" />
                </rule>
            </rules>
        </rewrite>
        <urlCompression doDynamicCompression="true" />
  </system.webServer>
</configuration>

[bangbingsyb]

@NemoDima
This is not a bug of IIS Compression - the gzip compression scheme (gzip.dll) shipped with IIS also have the same behavior. In fact, it is the design of IIS static and dynamic compression modules that leads to the behavior. The static and dynamic compression modules are responsible for reading the configs from applicationHost.config and web.config and pass the compression parameters (e.g. compression level) to the compression schemes (gzip.dll, iiszlib.dll, iisbrotli.dll etc).

Under httpCompression: only the MIME type collections staticTypes and dynamicTypes can be overridden. All other attributes under httpCompression is global only and can only be set in applicationHost.config. The ones in web.config will not be loaded to merge with the section in applicationHost.config.