Why I do have a white line (space) between content and footer?

For the start page I'm trying to just have one picture with primary navigation bar and footer:

Primary Navigation
Page content (just one picture with 100% width)
Footer (with 0 or 1 footer widget)

The issue is that I get a white line (space) between the picture and the footer.

Any idea how to get rid of this white line (space) between content and footer?
I don't know if this is an setup issue (even though I tried many different configurations) or if this might be a template design issue?

Thanks,
Mike.

Page Setup:
==========
Text:
<img src="URL/front_picture.jpg" alt="" width="100%" />

Disable Elements:
x Top Bar
x Header
Primary Navigation
x Secondary Navigation
x Featured Image / Page Header
x Content Title
Footer

Sidebar layout:
x Content (no sidebars)

Page Builder container
x Full Width

Themes Customizing:
==================
Content Layout: One Container
-> Content Padding or Separating Space shouldn't play a role in case of single container right?

Page source:
===========

`<div class="hfeed site grid-container container grid-parent">
<div class="site-content">

<div class="content-area grid-parent mobile-grid-100 grid-100 tablet-grid-100">
<main id="main" class="site-main">

<article id="post-20" class="post-20 page type-page status-publish" itemtype='http://schema.org/CreativeWork' itemscope='itemscope'>
<div class="inside-article">

<div class="entry-content">
<p><img src="URL/front_picture.jpg" alt="" width="100%" /></p>
</div><!-- .entry-content -->
</div><!-- .inside-article -->
</article><!-- #post-## -->

</main><!-- #main -->
</div><!-- #primary -->

</div><!-- #content -->
</div><!-- #page -->
<div class="site-footer ">`