Why is my nexus metadata.xml snapshot version incorrect?

I had this issue when I used the Maven Deploy Plugin and the Nexus Staging Plugin simultaneously. Try skipping the Maven Deploy Plugin:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-deploy-plugin</artifactId>
  <configuration>
    <skip>true</skip>
  </configuration>
</plugin>

I encountered the same problem. You might check your test-sdk's parent pom to see if any extra maven deploy plugin defined in.

I don't know why this happens, but I solved scheduling a Nexus task to "rebuild metadata" in "Scheduled Task" admin option. For now, this is a valid solution for me.

Additional information about how to fix the issue in this answer