i figured out a way to fix it, inside the plugin
it appears to be a problem with the
esc_url(get_pagenum_link($page + 1)
this is the fix
$nextlink = ($this->type === 'posts')
? esc_url(get_pagenum_link($page + 1))
: get_comments_pagenum_link($page + 1);
if($page == 1 && $this->type === 'posts' && $_GET['cat'] != ""){
$nueva_pag = get_query_var('paged') + 1;
$nextlink = get_category_link($_GET['cat']) . "&paged=" . $nueva_pag;
}
and the same for the loop for the links