[MediaWiki-l] Import failed: Error creating directory shellbox

I'm attempting to import XML dumps from several other Mediawiki wikis into a local install of MediaWiki running on XAMPP. Some files import fine, but many of them get the error 'Import failed: Error creating directory shellbox-bdd810ee1edf29b3'. Number at the end changes with each attempt. I'm running: MediaWiki 1.37.2 PHP 7.4.27 (apache2handler) MariaDB 10.4.22-MariaDB I have '$wgTmpDirectory = "C:\xampp\htdocs\mediawiki_manuals\images\temp";' set in LocalSettings.php. All of my mediawiki directories & subdirectories have full permissions. None of them are read-only. Not sure what the hang-up is. Thanks for any help