"Add another item" button click turns on validation for node form without validation

I have turned off clientside validation for my node forms. But when clicking the "add another item" button of a multi-value field, clientside validation is unexpectedly turned on for the complete form.

In my case I cannot save the form as it complains about a wrong date format then (the date is entered in DD.MM.YYYY format which clientside_validation doesn't seem to recognized which is why I turned it off). But this is another story.