Can’t you set the application to run across a unc path? Instead of looking at X:\data_source\data.db, can’t you set the app to look at \\serverB\data\data.db.
The best method is to not use a mapped drive as there is no way to guarantee that the mapped drive will always exist. The best method is to use the UNC path to access to remote access database.
And I must say, writing a data replication system in Microsoft access, that’s pretty hard core. I’m curious why you decided to stay in Microsoft access, instead of scaling up to Microsoft SQL Server Express which includes a very robust replication system?