When Environments are copied from in admin portal the dataflows are not copied or at least do not show up in the dataflow area. They do however exist in the Dataverse table called dataflows. because of this trying to import a solutions containing managed dataflow will fail with an obscure error. The only way to fix this is to delete the records form the dataflow table and re import the managed solution. The issue is that you can't delete data flow records that are marked as managed... If you can't copy the dataflows and make them available in the target environment, then the records for those dataflows in the dataflow table should be removed allowing the next solution import to import the dataflows.
Example the production environment is copied to a new UAT environment we then import the latest solution changes for testing, but the import fails because the dataflows are missing.