SQL 2012 Merge Replication data sync issues

We've got a publisher running SQL 2012 replicating the same database to 4 subscribers running 2012 Express. This database contains a table which stores the site name and a date stamp. If this datestamp is older than 30 minutes then we know that database is out of sync and can investigate (VPN down or whatever). The problem at the moment is replication monitor shows that one of these subscribers has data being uploaded and downloaded to it and transactions made on this database are being uploaded, and transactions on other database are being downloaded to it. However with this one table this site isn't uploading its datestamp. The other locations are updating their stamps to this table, but this one row isn't being replicated out.

Hope that all makes sense. Essentially we've got an issue where some data isn't being replicated. We've tried valaidating, main problem being any errors with validating don't show up, the sync monitor screen keeps going to "no response received in 10 minutes". Haven't seen anything in the main SQL log. If it successfully validates and this row gets transmitted across, it doesn't continue replicating. Reinitialization isn't an option currently. Hopefully someone's got some ideas.