The zookeeper dependency in pom.xml of several services references zookeeper with groupId org.apache.hadoop. This doesn't match the groupid in the zookeeper-3.3.1.pom, which causes our proxy to return a 409 with the following in the logs:
The target deployment path 'org/apache/hadoop/zookeeper/3.3.1/zookeeper-3.3.1.pom' does not match the POM's expected path prefix 'org/apache/zookeeper/zookeeper/3.3.1'. Please verify your POM content for correctness and make sure the source path is a valid Maven 2 repository root path.
Changing the dependencies to reference groupId org.apache.zookeeper fixes the problem.