You have the one-to-many list managed e.g. when you add an object to the list it sets the foreign key field as appropriate, you should set the collection to "managed"
. That you can achieve by opening the forward-mapping wizard clicking on the Items
field in the treeview on the left and than check the Manage Collection
This should solve the problem but if you require any other suggestions/clarifications we are here to help.
the Telerik team