There is a structural flaw in the footer tag of the site template:

<footer class="grid-child container-footer footer">
	<hr>
	<p class="float-right">
		<a href="#top" id="back-top" class="back-top">
			<span class="icon-arrow-up-4" aria-hidden="true"></span>
			<span class="sr-only"><?php echo Text::_('TPL_CASSIOPEIA_BACKTOTOP'); ?></span>
			</a>
		</p>
<jdoc:include type="modules" name="footer" style="none" />
	</footer>

Actual result

The "back-to-top" feature is in the same tag as a call to a module in a footer position. So, when one assigns a module to the footer position, the module content is kind of "glued" to the "back-to-top".
I guess the call to the module should be at least in another tag, maybe another footer.