Identity Management in a Pull Merge Replication at Subscriber

I am facing SQL Server Replication issue (Identity Management in a Pull Merge Replication at Subscriber).

Replication situation:

Distributor and the Publisher are in one server running Windows Server 2012 Std and SQL Server 2012 Std
One Subscriber PC running Windows 7 Professional and SQL Server 2012 Express Edition
Both are connected through the internet using VPN

The Problem:

Subscriber has an article (Table) [DocumentItems] where its Identity field [DocumentItemsID] is managed by Replication and was assigned the following range:

([DocumentItemsID]>(280649) AND [DocumentItemsID]<=(290649) OR [DocumentItemsID]>(290649) AND DocumentItemsID]<=(300649)

The server was disconnected from electricity several times. Every time the Subscriber PC is up, The [DocumentItemsID] field will pick an identity out of its range like 330035 when inserting new rows.

The issue happened 3 times. I fixed the problem by a manual reseed:

    DBCC CHECKIDENT('DocumentItems' , RESEED, xxxx)

Where xxxx is the MAX existing value for [DocumentItemsID] + 1

Once the electricity is disconnected again, the same problem occurs.

Does anybody have any idea what is happening? And why the [DocumentItemsID] field was assigned values out of its range?

Thanks