osTicket Version v1.12.3 (bcf1a6f) — Up to date
Web Server Software Apache/2.4.41 (Unix) OpenSSL/1.0.2g
MySQL Version 5.7.27
PHP Version 5.6.40

I understand that to clean up attachments on the filesystem, the cron job needs to be run as mentioned in this post:
https://forum.osticket.com/d/88259-attachment-files-not-deleting

I've tried the following:
Running cron.php via the cli: php srv/users/####/apps/####/public/support/api/cron.php
Running http://www.MYSITE.COM/rcron.php via http:

• Updated the URL inside rcron.php to http://www.MYSITE.COM/support/api/tasks/cron
• Added and API key generated for my server's IP in rcron.php (with "can execute cron" checkbox enabled)
• Changed the rcron.php file's permissions to 0755

this outputs "#!/usr/bin/php -q" in the browser

After trying both methods of running cron a couple of times, the attachments from the deleted tickets are still present on the server.
Can you advise on how to troubleshoot this further?

Greetings,
Manuel