This is the field I have

piklist('field', array(
    'type' => 'group',
    'field' => 'slides',
    'label' => __('Slides'),
    'template' => 'field',
    'list' => false,
    'add_more' => true,
    'fields' => array(
        array(
            'type' => 'file',
            'field' => 'image',
            'columns' => 12,
            'options' => array(
                'modal_title' => __('Select image', 'app'),
                'button' => __('Select image', 'app')
            )
        ),
        array(
            'type' => 'text',
            'field' => 'title',
            'columns' => 6,
            'attributes' => array(
                'placeholder' => 'Title'
            )
        ),
        array(
            'type' => 'text',
            'field' => 'link',
            'columns' => 6,
            'attributes' => array(
                'placeholder' => 'URL (optional)'
            )
        ),
        array(
            'type' => 'textarea',
            'field' => 'content',
            'columns' => 12,
            'attributes' => array(
                'rows' => 3,
                'placeholder' => 'Description'
            )
        ),
    )
));

When creating a post, the image is not saved (the rest of the fields are) but if I populated the field directly in the DB and edit the post everything works fine.

It doesn’t save the image if, from an existing post, I delete the image and try to add again.

From what I saw the problem is that the _post_meta[slides][0][image][] input fields are not updated correctly. When you remove the image the value of the associated field is cleared, but the input stays on the homepage and when you add an image there is not input field appended to the DOM.

I think this might cause problems with ALL the image selector fields not just in the repeater.