Hello,
I experienced the same kind of problem.
In a merge replication with SQL Express 2012, I got the error when applying the snapshot to the subscriber.
On server side, the database file is about 7.5 Gb.
Strange fact ... at the moment of the error : my database file (on the subscriber) is exactly sized to 4Gb but ... I read somewhere SQL Express 2012 file limitation was extended to 10Gg ...
An idea ?
Kind regards