Simply Static is not deleting temporary files after use

If you notice that temporary files used by Simply Static are not being deleted properly in your hosting environment, you should first check to make sure that file permissions for the directory are set correctly. To allow a program to read, write, and delete files and directories in PHP, you could set the permissions to 775.

If setting the permissions to a new value does not resolve the issue you could try adding the following Simply Static action to the functions.php file of your active child theme and running a new full export.

add_action( 'ss_before_static_export', function ( $blog_id, $job ) {
	$options  = get_option( 'simply-static' );
	$temp_dir = $options['temp_files_dir'];

	// Delete all files inside the temporary directory.
	glob( $temp_dir . '/*' );
}, 10, 2 );

Here is a link to more information on using a Simply Static action filter in WordPress: https://docs.simplystatic.com/article/24-how-to-use-a-filter-in-wordpress