Unable to save product settings for optional quantity field

Found problem ...
I have two modules enabled .. product attributes and File downloads

When I uninstalled file downloads ..Save settings worked.

One more observations ..

these two buttons are present in form ..

<input data-drupal-selector="edit-submit" type="submit" id="edit-submit" name="op" value="Save configuration" class="button button--primary js-form-submit form-submit">   --> from file downloads .. works

<input data-drupal-selector="edit-submit" type="submit" id="edit-submit--2" name="op" value="Save configuration" class="button button--primary js-form-submit form-submit"> --> Save setting main submit button dont work. 

Its like form inside form..

<form class="uc-product-settings-form" data-drupal-selector="uc-product-settings-form" action="/divyam/code/admin/store/config/products" method="post" id="uc-product-settings-form" accept-charset="UTF-8">
    <form class="uc-file-feature-settings-form" data-drupal-selector="uc-file-feature-settings-form" action="/divyam/code/admin/store/config/products" method="post" id="uc-file-feature-settings-form" accept-charset="UTF-8">

    </form>
 </form>   

ok.. It looks like in Dev version .. file settings has been moved to separate settings page. so this will be fixed in new version. thanks