Failed to open stream: File Exists?

[MGParisi]

Warning: fopen(C:\wamp64\www\xxxx\wp-temp\xxxx\logs\log_2018-05-14.txt): failed to open stream: File exists in C:\wamp64\www\xxxx\wp-content\plugins\xxxx\vendor\katzgrau\klogger\src\Logger.php on line 167

This is run through the earlier class and is attempting to open with an 'a' attribute.

[MGParisi]

37	7.9236	78582472	project\system\notify->__construct( )	...\base.php:37
38	7.9236	78583560	Katzgrau\KLogger\Logger->__construct( )	...\notify.php:68
39	7.9238	78583656	Katzgrau\KLogger\Logger->setFileHandle( )	...\Logger.php:130
40	7.9238	78583656	fopen ( )	...\Logger.php:167

Sorry, can not provide access.. I can say this is on a Windows platform and that I created the directory with

    if (!is_dir($log_dir)) {
        $oldmask = umask(0);
        mkdir($log_dir,0777, true);
        umask($oldmask);
        chmod($log_dir, 0777);
    }

Also the log is in a parent directory.