All values of quantity fields are reset, in grid with quantity fields per attribute, at the product page

[netfuchs]

Hi all
Prestashop version is 1.7.4.2
On the product page I want to show product-attributes in a grid, with the possibility to insert the quantity per attribute and to add this to the cart.

Problem is: after changing the quantity in one of the fields, the inserted value will be reset and the order of the attribute rows will be changed.

I have modified the file /themes/classic/templates/catalog/_partials/product-variants.tpl.
As the result, I have one line per attribute, with a quantity field and an add-to-the-cart button per row.
I have also erased the quantity field at the page ../catalog/product.tpl, but this had no effect to the behaviour.
I have also modified or erased the functions of product.js and theme.js, but i didn't notice any impact.

 

 

/themes/classic/templates/catalog/_partials/product-variants.tpl looks like this:

<div class="product-variants">
  {foreach from=$groups key=id_attribute_group item=group}
    <div class="clearfix product-variants-item">
      <span class="control-label">{$group.name}</span>
      <row>
        <table class="table-product-discounts">
          {foreach from=$combinations key=id_attribute item=group_combinations}
            <tr>
              <td>{$group_combinations.attributes_values.1}</td>
              <td>{math equation="x + y" x=$productPriceWithoutReduction y=$group_combinations.price}</td>
              <td><form autocomplete="off" name="formlist{$group_combinations.attributes.0}" action="             					{$urls.pages.cart}" method="post">
                  <input type="hidden" name="token" value="{$static_token}">
                  <input type="hidden" value="{$product.id_product}" name="id_product" id="id_product">
                  <input type="hidden"
                         data-product-attribute="{$group_combinations.attributes.0}"
                          name="id_product_attribute"
                          value="{$group_combinations.attributes.0}">
                  <input type="number"
                          style="padding: 11px 10px; float:left; width: 40%;
                         class="input-group form-control"
                          data-product-attribute="{$group_combinations.attributes.0}"
                          name="qty{$group_combinations.attributes.0}"  min="1" value="1">

                  <button
                          class="btn btn-primary list-btn" data-button-action="add-to-cart"
                          type="submit"
                  >
                    <i class="material-icons shopping-cart">&#xE547;</i>
                  </button>
                </form> </td>
             </tr>
          {/foreach}
        </table>
      </row>
    </div>
  {/foreach}
</div>

Any help is highly appreciated. Thank you.

Edited November 9, 2018 by netfuchs
URL to test page removed (see edit history)