An error occurred when deleting the cache file

When multiple requests are sent to the server at the same time. The following error occurs.

Why is it not checked that the file exists when the file is about to be deleted?
Is it possible that an earlier process has deleted the file in processes that occur simultaneously?

while (false !== ($filename = readdir($dh))) {
            if (empty($filename)) {
                continue;
            }
            if ($filename[0] === '.') {
                continue;
            }
            $key = substr($filename, 0, strlen($filename) - 4);
            if ($this->isOld($key, $config)) {
                unlink($dir . '/' . $filename);
            }
        }

Why package version 4.17 registered but cache file version is 4.15?

class HTMLPurifier_Config
{

    /**
     * HTML Purifier's version
     * @type string
     */
    public $version = '4.17.0';
    
}

Web server: nginx
Php : 8.2
Package: "ezyang/htmlpurifier": "^4.17.0"

Start by tracing the cache cleanup loop containing readdir(), isOld(), and unlink(), then inspect how concurrent requests and the reported package/cache versions are handled. Reproduce the deletion error with multiple simultaneous requests; done means the failure is understood and the cache cleanup behaves correctly.