I'm not sure I follow you, are you creating the Group in live data source and then switching to Extract? You'll have to create the extract again when you make changes. Or, you can just create the grouping in Extract itself.

To follow on from Shivaram's question, what do you mean by "replaced"?

Are you refreshing the data in the extract, or are you doing a "Replace data source" activity?  If you're doing the latter, that's likely the cause of the issue.