A replicated database (either a replica or Design Master) cannot be saved as an MDE file. To save a replicated database as an MDE file, you must first remove replication.
Once a database is saved as an MDE file, it can be replicated; however, replication is only recommended in situations where no further changes need to be made to the original database. There is no way to make changes to the design of forms, reports, or code in the Design Master MDE file, and design changes made in the original database can't be synchronized with pre-existing MDE replicas. For this reason, if you need to make a design change to a replica set of MDE files, you must make that change in the original database, resave it as an MDE file, and then create and distribute an entirely new replica set from the new MDE file.