When using Grid custom editor, the Kendo Editable adds data-binding for the value for both the hidden and the visible inputs of the ComboBox. This results in a field named [propertyName]_input to appear in the item model after it has been edited.

The way this happens is a bit inconsistent and depends on setup, but in the linked dojo, using tab after editing causes this to happen, but in our applications pressing enter  and sometimes even clicking off the editor causes this issue. 

Reproduction of the problem

• Go to the following Dojo sample; https://dojo.telerik.com/OfiCoyog
• Edit the category column and wait for the combobox.
• Type free text, without selecting a value;
• Press tab - the value won't be updated. Also, if you look at the Item, it will have a Category_input field, that has been added, while editing;

See here for the original bug. https://github.com/telerik/kendo-ui-core/issues/3427#issue-244359311