Invalid content returned through proxy prevents valid content from being retreived

In a stock configuration of Nexus, retreive https://localhost:8081/repository/maven-central/ant/ant/maven-metadata.xml.

Set up Charles Proxy as the http proxy for outbound requests.  Using a rewrite rule, make it so that requests to repo1.maven.org return invalid content with a 200 response.

Invalidate cache on the maven-central repository.

Request  https://localhost:8081/repository/maven-central/ant/ant/maven-metadata.xml again.

Observe in the logs:

2020-03-31 16:10:55,911-0500 WARN  [qtp2069272095-57] *UNKNOWN org.sonatype.nexus.repository.view.handlers.ExceptionHandler - Invalid content: GET /ant/ant/maven-metadata.xml: org.sonatype.nexus.repository.InvalidContentException: Metadata at path ant/ant/maven-metadata.xml is not a valid maven-metadata.xml

But also observe... the content has been lost in Nexus Repo! See screenshot below.

Expected: Invalid content should be served when valid content is available. The whole point of the file content validation feature is to prevent this from happening.

Workaround: Check "Block outbound connections on the repository" in the proxy repository. This will allow previously cached content to be served.