Media object fetch image failed

Hi all,
We are using E19.1 on red hat Linux. Having an issue with attachments. While some of the attachments (pdf) are viewable in the address book and at invoices, some while clicking the attachment to view gives this error: “Media object fetch image failed” I then looked at the media queue directory in the file system the file does exist. I have to copy this to local pc and delete the inaccessible attachment in JDE and reupload the attachments. This is very cumbersome and I really appreciate your help in resolving this annoying issue. Many thanks in advance.