Hi Donald,

adjusting the code like this should work:

$img_block_counter = 0;
foreach ( $blocks as $block ) {
	if ( 'core/image' === $block['blockName'] && $img_block_counter === 0 ) {
		$img_block_counter++;
		continue;
	} else {
		$content_markup .= render_block( $block );
	}
}

Hope that helps!
Florian