You do understand that the issue has something to do with the Attachments on the Filesystem plugin, yes?
If I had a solution for you I would gladly offer it. But I don’t know what the problem is, and it is beyond the support that I can offer for osTicket Awesome.
Make sure you’ve installed the latest version of the plugin (osTicket Awesome should have the latest version, unless you copied it from somewhere else).
Make sure you’re running osTicket Awesome for osTicket 1.16.x make sure you’re also running PHP 8.0.x and not PHP 8.1.x or anything higher.
If you’re still having trouble I would suggest reporting your issue on the osTicket > Plugins Github page.
I hope this helps!