We’re adding validations for listings with variations. This is because we were accepting numbers in cases when a String is required, according to our Documentation. From next monday, November 10th on, we’ll only accept the value you send for attribute_combinations as a String, so if you’re sending another data type we suggest you adapt your system as soon as possible.
If you want to learn how to work with variations, check the List with variations and Modify item with variations tutorials.
If you have any doubts, please go to our forum.