Editing Content with DataGridField in Modal

Does anyone have a working example of editing content items with z3c datagridfield in modal overlay ?

I have a modal to edit some (related) content-items and a datagridfield.

Now, I have added another data grid field to the same content type and I run into this problem:

With auto-append of rows, TWO new rows are added instead of one (if I add 3 datagridfields to my content type, 3 new fields are added ).

So, to solve this, I decided to drop 'auto-append' and instead use the add row button. The problem is: the content gets automatically saved.

Do all the instances have unique IDs?