multiple img field: thumbs are all 1st image

Problem/Motivation

Steps to reproduce

This is a multiple image field configured like that :

content:
  field_image_produit:
    type: slick_image
    label: hidden
    settings:
      caption:
        title: '0'
        alt: '0'
      optionset: mmaw_caroussel_image_produits
      icon: ''
      layout: ''
      view_mode: ''
      cache: -1
      current_view_mode: default
      skin: ''
      fx: ''
      style: ''
      background: false
      box_caption: ''
      box_caption_custom: ''
      box_media_style: ''
      responsive_image_style: ''
      box_style: ''
      image_style: image_produit_slide
      media_switch: ''
      ratio: ''
      thumbnail_style: image_produit_menu
      _uri: ''
      breakpoints: {  }
      sizes: ''
      grid_header: ''
      grid: null
      grid_medium: null
      grid_small: null
      overridables:
        arrows: '0'
        autoplay: '0'
        dots: '0'
        draggable: '0'
        infinite: '0'
        mouseWheel: '0'
        randomize: '0'
        variableWidth: '0'
      optionset_thumbnail: ''
      skin_thumbnail: ''
      thumbnail_caption: ''
      thumbnail_effect: grid
      thumbnail_position: ''
      override: false
      skin_arrows: ''
      skin_dots: ''
      use_theme_field: true
      preserve_keys: false
      visible_items: null
    third_party_settings: {  }
    weight: 2
    region: content

If I inspect the html:

<div data-thumb="/sites/default/files/styles/image_produit_menu/public/2021-10/Ride_Cligno_G%402x_0.png?h=dcd7f4fc" class="media media--blazy media--slick media--image is-b-loading">

data-thumb is the same for all 4 images

I'll try to look if I can find a solution and update

Thanks for the awesome module !