Incorrect npm metadata reported when using group repository

Issue: 

When querying npm metadata via NPM Group repository, getting undefined errors as below.

[root@centos79 nvm]# npm show serve@* version --registry=http://localhost:8081/repository/npm-group
undefined@11.3.0 '11.3.0'
undefined@9.2.0 '9.2.0'
undefined@6.5.7 '6.5.7'
undefined@6.5.8 '6.5.8'

Upon using NPM Proxy repository, the same works fine

[root@centos79 nvm]# npm show serve@* version --registry=http://localhost:8081/repository/npm-proxy
serve@0.0.1 '0.0.1'
serve@0.0.2 '0.0.2'
serve@0.0.3 '0.0.3'
serve@0.0.4 '0.0.4'

 Reproduce Steps: 

1. Create a npm-group repo with npm-proxy and npm-hosted repo. 
2. Query version of any public modules using npm group repo
3. Query the same module using npm proxy repo

Expected Behavior: Expecting the npm group repo output to provide actual module versions, same as npm-proxy repo.