Remove accents from Wordpress uploads. This renames all files and replaces corresponding attachment in WordPress database. This helps to avoid possible problems with *EXITSTING* filenames. To avoid this in future install mu-plugin which hooks in 'sanitize_file_name'

wp-rename-uploads.php

<?php
/**
 * Replace-uploads.php
 * This replaces all accents from your uploads
 * you can run this with wp-cli: $ php wp-cli.phar eval-file rename-uploads.php
 *
 * You may need to run the outputted move commands in order to update the filenames.
 */

if ( ! defined( 'WP_CLI' ) || ! WP_CLI ) {
	// Bail.
	exit;
}

// Change to right path before making changes.
if ( defined( 'WP_CONTENT_DIR' ) ) {
	chdir( WP_CONTENT_DIR );
} else {
	chdir( ABSPATH );
}

// Get all uploads.
$uploads = get_posts(
	array(
		'post_type'   => 'attachment',
		'numberposts' => -1,
		'include'     => array( _______POST_IDS_HERE________ ), // TODO.
	)
);

global $wpdb;

// Get upload path.
$path = wp_upload_dir()['basedir'];

echo 'Found: ' . count( $uploads ) . " attachments...\n";
echo "This may take a while...\n\n";

// Loop through all upload images.
foreach ( $uploads as $upload ) {
	// Reset flag.
	$replace_name = false;

	foreach ( get_post_meta( $upload->ID, '_wp_attached_file', false ) as $index => $file ) {
		echo "# Processing ID: {$upload->ID}\n";
		$full_path       = $path . '/' . $file;
		$ascii_file      = strtolower( preg_replace( '/[^a-zA-Z0-9\/\-\_\.]/', '', ( remove_accents( $file ) ) ) );
		$ascii_full_path = $path . '/' . $ascii_file;

		// This replaces main file.
		if ( $file !== $ascii_file ) {
			$replace_name = true;
			echo "mv '{$full_path}' {$ascii_full_path}\n";

			// NOTE: This doesn't seem to work in some cases.
			rename( utf8_decode( $full_path ), $ascii_full_path );

			// Also replace the thumbnails versions.
			$file_path = dirname( $full_path );
			$metadata  = get_post_meta( $upload->ID, '_wp_attachment_metadata', false )[ $index ];

			// Update main file.
			$metadata['file'] = $ascii_file;

			if ( isset( $metadata['sizes'] ) ) {
				foreach ( $metadata['sizes'] as $name => $thumbnail ) {
					$metadata['sizes'][ $name ]['file'];
					$thumbnail_path  = $file_path . '/' . $thumbnail['file'];
					$ascii_thumbnail = strtolower( preg_replace( '/[^a-zA-Z0-9\/\-\_\.]/', '', ( remove_accents( $thumbnail['file'] ) ) ) );

					// Update metadata on thumbnail so we can push it back to database.
					$metadata['sizes'][ $name ]['file'] = $ascii_thumbnail;

					$ascii_thumbnail_path = $file_path . '/' . $ascii_thumbnail;
					echo "mv {$thumbnail_path} {$ascii_thumbnail_path}\n";

					// NOTE: This doesn't seem to work in some cases.
					rename( utf8_decode( $thumbnail_path ), $ascii_thumbnail_path );
				}
			}

			$fixed_metadata        = serialize( $metadata );
			$file_basename         = basename( $file );
			$replace_file_basename = basename( $ascii_file );

			// Replace in DB...
			// Replace main file.
			$sql = "UPDATE {$wpdb->prefix}postmeta SET meta_value = '{$ascii_file}' WHERE post_id={$upload->ID} and meta_key='_wp_attached_file';";
			$wpdb->query( $sql );

			// Replace thumbnail fields.
			$sql = "UPDATE {$wpdb->prefix}postmeta SET meta_value = '{$fixed_metadata}' WHERE post_id={$upload->ID} and meta_key='_wp_attachment_metadata';";
			$wpdb->query( $sql );

			// Space out each set of commands.
			echo "\n";
		}
	}
}