Smush PNG to JPG, Update image paths for converted images in case it wasn't updated by plugin. Make sure to enable debug log, in order to have a log of what all images are updated.

smush_png_jpg_update_path.php

<?php
add_action('current_screen', 'smush_update_image_url');

function smush_update_image_url() {
	global $wpsmush_db;
	if( !function_exists('get_current_screen')) {
		return;
	}
	$current_screen = get_current_screen();
	if( empty( $current_screen ) ) {
		return;
	}
	$current_page   = $current_screen->base;
	echo "<!-- $current_page -->";
	if ( 'media_page_wp-smush-bulk' != $current_page ) {
		return;
	}
	if( is_object( $wpsmush_db ) ) {
		//get the list of converted images
		$converted_images = $wpsmush_db->converted_images();
		echo "<!-- <pre>";
		print_r( $converted_images );
		echo " </pre> -->";
		if( is_array( $converted_images) && !empty( $converted_images ) ) {
			//Iterate through all the image ids and Update the image URL in post content
			foreach ( $converted_images as $image ) {
				$updated = smush_replace_url( $image );
			}
		}
	}
}
//Iterate over image size to request url update in post content of an attachment
function smush_replace_url( $id ) {
	//Current file URL
	$c_url = wp_get_attachment_url( $id );
	$filepath = get_attached_file( $id );
	//Get the original file path
	$original_file = get_post_meta( $id, WP_SMUSH_PREFIX . 'original_file', true );
	$pngjpg_savings = get_post_meta( $id, WP_SMUSH_PREFIX . 'pngjpg_savings', true );
	//Return early if there are no pngjpg savings
	if( empty( $pngjpg_savings) || !is_array( $pngjpg_savings ) ) {
		return;
	}
	$metadata = wp_get_attachment_metadata( $id );
	$sizes = array();
	if( !empty( $metadata ) && !empty( $metadata['sizes'] ) ) {
		$sizes = $metadata['sizes'];
	}
	if( empty( $original_file ) ) {
		//Get GUID
		$guid = get_the_guid( $id );
	}
	$basename =  !empty( $original_file ) ? basename( $original_file ) : basename( $guid );
	$base_url = dirname( $c_url );
	$png_url    = $base_url . '/' . $basename;
	//Iterate over various converted sizes of an attachment
	foreach ( $pngjpg_savings as $image_size => $savings ) {
		//If there are no savings, skip
		if ( empty( $savings ) ) {
			continue;
		}
		if ( 'full' == $image_size ) {
			$file_png = str_replace( basename( $filepath ), basename( $png_url ), $filepath );
			if ( empty( $c_url ) || empty( $png_url ) || !file_exists( $file_png ) ) {
				continue;
			}
			$updated = smush_update_url( $png_url, $c_url );
		} elseif ( key_exists( $image_size, $sizes ) ) {
			//Only if the image size is available in registered image sizes list
			$file = $sizes[ $image_size ]['file'];
			echo "<!--" . $file . "-->";
			$info = pathinfo( $file );
			if ( ! empty( $info['filename'] ) ) {
				//Old PNG URL
				$image_url = $base_url . '/' . $info['filename'] . '.png';
				//Get the current URL for image size
				$c_url = str_replace( basename( $c_url ), $file, $c_url );
				$filepath = str_replace(basename($filepath), $file, $filepath );

		      		$file_png = str_replace( basename( $filepath ), basename( $image_url ), $filepath );

				if ( empty( $c_url ) || empty( $image_url ) || !file_exists( $file_png ) ) {
					continue;
				}
				$updated = smush_update_url( $image_url, $c_url );
			}
		}
	}
}
//Perform the replacement
function smush_update_url( $o_url, $c_url ) {
	//Update In Post Content, Loop Over a set of posts to avoid the query failure for large sites
	global $wpdb;
	//Get existing Images with current URL
	$file = str_replace(site_url(), '', $o_url );
	$replace = str_replace(site_url(), '', $c_url );
	$query = "SELECT ID, post_content FROM $wpdb->posts WHERE post_content LIKE '%$file%' LIMIT 10";
	echo "<!--" . $query . '-->';
	$rows = $wpdb->get_results( $query, ARRAY_A );
	if ( empty( $rows ) || ! is_array( $rows ) ) {
		return false;
	}
	echo "<!-- <pre>";
	print_r( $rows );
	echo " </pre> -->";
	//Iterate over rows to update post content
	foreach ( $rows as $row ) {
		// replace old URLs with new URLs.
		$post_content = $row["post_content"];
		$post_content = str_replace( $file, $replace, $post_content );
		// Update Post content
		return $wpdb->update(
			$wpdb->posts,
			array(
				'post_content' => $post_content,
			),
			array(
				'ID' => $row['ID'],
			)
		);
	}
}
?>