Reproduced on the online demo with AllowMultiColumnSorting enabled on the MasterTableView. http://demos.telerik.com/aspnet-ajax/persistence-framework/examples/custom-storage-provider/defaultcs.aspx
This bug was fixed in Q1 2014 SP1
This needs to be fixed as we have ran across this as well. Ticket ID #857918 has complete details.
Can you please fix that?