Featured images on post navigation not correct

Hi Guys

Following this post https://generatepress.com/forums/topic/featured-image-in-pre-next-post-navigation/
I’ve managed to add featured images to my post nav, but I have a small problem that I hope you can help with.

On many posts the images are not matching the target post.

Here are the 3 snippets I’m using to control the post nav

add_action( 'after_setup_theme', 'tu_category_specific_post_navigation' );
function tu_category_specific_post_navigation() {
    add_filter( 'generate_category_post_navigation', '__return_true' );
}

add_filter( 'generate_category_list_output', function( $output ) {
    if ( !is_single()) {
        return $output;
    }
    return '<span class="category-label">Read More:</span>' . $output;
} );

add_filter( 'generate_post_navigation_args', function( $args ) {
    if ( is_single() ) {
        $prevPost = get_previous_post();
        $prevThumbnail = isset( $prevPost ) ? get_the_post_thumbnail( $prevPost->ID ) : '';
        $nextPost = get_next_post();
        $nextThumbnail = isset( $nextPost ) ? get_the_post_thumbnail( $nextPost->ID ) : '';

        $args['previous_format'] = '<div class="nav-previous">' . $prevThumbnail . generate_get_svg_icon( 'arrow' ) . '<span class="prev" title="' . esc_attr__( 'Previous', 'generatepress' ) . '">%link</span></div>';
        $args['next_format'] = '<div class="nav-next">' . $nextThumbnail . generate_get_svg_icon( 'arrow' ) . '<span class="next" title="' . esc_attr__( 'Next', 'generatepress' ) . '">%link</span></div>';
    }

    return $args;
} );

And here is my css

/* Post Navigation */
.site-main .post-navigation {
	margin-top: 1em;
	padding: .5em;
	width: 100%;
  border: 1px solid #f2f2f2;
  border-radius: 10px;
	
}

.post-navigation img {
	  width: 200px;
    display: inline-block;
    vertical-align: middle;
    margin: 0 5px;
}

/* switch next > to after title */
.nav-next .next:after {
    font-family: GeneratePress;
    text-decoration: inherit;
    position: relative;
    margin-left: .6em;
    width: 13px;
    text-align: center;
    display: inline-block
}

.post-navigation .nav-previous,
    .post-navigation .nav-next {
        display: flex;
        flex-direction: column;
        margin-bottom: 5px;
}

/* flex row for desktop and tablet */
@media (min-width: 420px) {

    .post-navigation {
        display: flex;
    }
    .post-navigation .nav-next {
        margin-left: auto;
        align-items: flex-end;
        text-align: right;
    }
}

@media (max-width: 769px) {
.post-navigation img {
    width: 300px;
}
}

.nav-previous, .nav-next {
    position: relative;
}
.nav-previous a:before, .nav-next a:before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

On the css, I also need help to get the arrow to show on the same line as the title ;-)

Thanks
Brian