• We have had the same issue (SQL Server 2012, SP3) and we think it's because of this:

    The NOT FOR REPLICATION option is specified by default for foreign key constraints and check constraints; the constraints are enforced for user operations but not agent operations.


    Source: https://docs.microsoft.com/en-us/sql/relational-databases/replication/administration/frequently-asked-questions-for-replication-administrators

    Also some further information about IDENTITY columns in a replication scenario:

    https://docs.microsoft.com/en-us/sql/relational-databases/replication/publish/replicate-identity-columns