Binding DVDropdownList to Text field

Question

I'm trying to save a selection from a DVDropDownList to a text field but when selecting an option and saving the new item, the textfield remains empty.

<SharePoint:DVDropDownList runat="server" id="ff13{$Pos}" ControlMode="New" FieldName="InteractionContact" __designer:bind="{ddwrt:DataBind('i',concat('ff13',$Pos),'SelectedValue','SelectedIndexChanged','ID',ddwrt:EscapeDelims(string(@ID)),'@InteractionContact')}"/>

I changed element from SharePoint:FormField to SharePoint:DVDropDownList which is dynamically populated at runtime by JavaScript (retrieving a dynamic subset of values from another list). Everything else remains the same. What's missing for the selected value on the Dropdown to save to the text field?

Edit I've tried using

TextChanged

As eventhandler too, no change.