Database error for <GET DATA FROM KPRO>

[#1]

Hi,
I get  Database error for <GET DATA FROM KPRO> when trying to access an attachment in ME23N.

I have seen that it can be caused by insufficient modification of one of the following RFC destinations:

• SAPHTTP
• SAPHTTPA
• SAPFTP
• SAPFTPA

However this only happens to some POs and not all POs and this only occurs for some attachments and not all attachments. There does not seem to be any pattern as to why I would get this error as well. On some days I can open the attachment and some days I cannot. If anyone can suggest any answers, that would be most appreciated. 

Thank you.