were are using ProGet Enterprise Edition Version 2026.14 (b-11.l+pe) in a Linux Docker installation.
After the upgrade from 2026.12 to 2026.14 our builds fail to download remote Maven artifacts, if the connector artifact cache is disabled.

I created an example feed 'maven-test', with the default connector to 'maven.org' and connector artifact cache disabled (see screenshot).

When I try to download a Maven artifact (for example the 'maven-source-plugin'), I get a server error 500 for the POM or the JAR.

https://registry.my-company.com/maven2/maven-test/org/apache/maven/plugins/maven-source-plugin/3.3.1/maven-source-plugin-3.3.1.jar
=> HTTP code 500

https://registry.my-company.com/maven2/maven-test/org/apache/maven/plugins/maven-source-plugin/3.3.1/maven-source-plugin-3.3.1.pom
=> HTTP code 500
Response: Specified method is not supported.

When I enable caching, the download works again with the same URLs.

The diagnostic center shows the following message:

An error occurred processing a GET request to http://registry.my-company.com/maven2/maven-test/org/apache/maven/plugins/maven-source-plugin/3.3.1/maven-source-plugin-3.3.1.pom: Specified method is not supported.

System.NotSupportedException: Specified method is not supported.
   at System.Net.Http.HttpBaseStream.get_Length()
   at Inedo.ProGet.WebApplication.FeedEndpoints.Maven.SubHandlers.ArtifactDownloadHandler.ProcessRequestAsync(AhHttpContext context, WebApiContext apiContext, Maven2Feed feed, ParsedMavenPath parsedUrl) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E658395\Src\src\ProGet\WebApplication\FeedEndpoints\Maven\SubHandlers\ArtifactDownloadHandler.cs:line 26
   at Inedo.ProGet.WebApplication.FeedEndpoints.Maven.MavenFeedHandler.ProcessRequestAsync(AhHttpContext context, WebApiContext apiContext, Feed feed, String relativeUrl) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E658395\Src\src\ProGet\WebApplication\FeedEndpoints\Maven\MavenFeedHandler.cs:line 86
   at Inedo.ProGet.WebApplication.FeedEndpoints.FeedEndpointHandler.FeedRequestHandler.ProcessRequestAsync(AhHttpContext context) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E658395\Src\src\ProGet\WebApplication\FeedEndpoints\FeedEndpointHandler.cs:line 205

::Web Error on 11/02/2026 16:24:14::

Background: We sometimes use feeds with attached local connectors to provide virtual repositories to our teams. For these aggregator feeds the cache is disable to prevent duplicate objects stored in the filesystem.