How to properly clean Merge Replication Setup
Somehow you are ending up with orphaned replication metadata after deleting the subscriptions and/or the publication.  This can happen when using the GUI to drop subscriptions and publication.  Instead, try using T-SQL replication stored procedures to delete the subscriptions and publication.

How to: Delete a Push Subscription (Replication Transact-SQL Programming)

How to: Delete a Pull Subscription (Replication Transact-SQL Programming)

How to: Delete a Publication (Replication Transact-SQL Programming)

After deleting the subscriptions and publication, verify the replication metadata was removed.  If not, use sp_removedbreplication to remove all replication objects from the databases.