Not for everyone - here is an example of an event with attachments
https://baza.cn.ua/admin/shop/event/44720/But I saw the same problem that I had earlier in a similar topic - you have some folders in / media / have a group under root - this means that cron was run manually as root. And this problem has not been fixed.
I remember that you pointed out that allegedly "our inexperienced employees did this" - unlike you - our "inexperienced employees" do not have SSH access to client servers, everyone else has clearly from the user under which they work onebox.
And I immediately warn you - we will not "throw sticks" at each other "who is to blame." At least I won't react to it.
If there are 2 solutions:
1. You change the owner and group of subfolders in the folder (to those under which onebox works) /media/ using the system administrator who maintains your server
2. We will provide you with a solution by means of our regular system administrator - it will be at the cost of 1 hour of revision.
PS: "tell me what to do - I'll do it myself" - this is also practically providing a solution.