All POM's within the Weld project are without a XML declaration like:
It would be good to add it.
This causes problems with Nexus3 which does not mirror Weld artifacts when "Strict Content Type Validation" is enabled on a repository which is the default.
The POM is correctly loaded from the upstream repository with content-type application/xml, but the mime type detection of Nexus 3 inspects the POM and concludes it is not an XML document due to the missing XML declaration.
See nexus.log for the detailed logging.