smart edit can't add new item to custom component

I want to add a new item from smart edit to my custom component but when I save the changes the item disappears. The item was created beacause I can add it from backoffice but not from smart edit. I try the same in other projects and it works successfully, maybe, because the components are OOTB and mine is customized.

I can't remove any item neither. The same thing happens,it seems like it works but when I save the changes there are no changes

There are no errors in terminal and we're using Hybris 18.08

Any suggestion?