<rule name="Add trailing slash" stopProcessing="true">
              <match url="(.*[^/{2,}])$" ignoreCase="true" />
              <conditions>
                <add input="{REQUEST_URI}" pattern="^/umbraco/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/api/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/install/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/App_Plugins/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/media/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/swagger/" negate="true" />
                <add input="{REQUEST_URI}" pattern="^/([0-9]+).aspx" negate="true" />
                <add input="{URL}" pattern="^.*\.(css|js|jpg|jpeg|png|gif|mp3|html|htm|xml|txt|pdf|svg|ico|json|webmanifest)$" negate="true" ignoreCase="true" />
              </conditions>
              <action type="Redirect" redirectType="Permanent" url="{R:1}/" />
            </rule>

I have this rule in a u10 site to try to force a trailing slash. I have also put

"RequestHandler": {
        "AddTrailingSlash": true
      }

in appsettings. It works on the front end but in the back end I am getting a constant stream of red errors: Request error: The URL returned a 404 (not found): /App_Plugins/uSkinned/views/truefalseshowhide-editor.html and the likes. I thought the would sort that out but apparently not?