Have a problem with wordpress, one of the website users is unable to upload PDF files to Media Library. User get's an error "Unexpected error from the server. The file may have been uploaded succesfully. Check in Media Library or reload the page" (https://i.stack.imgur.com/N1gbJ.png)
User is able to upload other file formats like jpeg, but not PDFs. This is happening for one user only, while other users able to upload any files.
We have an IP filter, allowing uploads only from designated IPs, but since she is able to upload jpegs, this shouldn't be the case.
User has admin rights so that shouldn't be an issue either.
Has anyone ever come across something like this? Any ideas why and how can this be fixed?
Thanks!