In my project there was a case when external storage was not available.
At that moment, users opened attachments and get empty window.
When the repository was restored, the records in the AD_Attachment were deleted.
1) Create Storage (image-1)
2) Restart server
3) Create attachment for any record
4) Close window with record
5) Simulate storage not available. Example remove attachment in storage
6) Open record (image-2).
7) Press button Attachment
8) Open empty attachment window
9) Close attachment window. Close window with record.
10) Simulate storage available. Example revert removing attachment
11) Open record. Attachment not found!
Palich.ru Development Team