When I tried to attach a file with a very long filename to an item in Zotero (Firefox, file syncing with WebDAV) the attachment does not appear, but the count in the '+' column increments. If I rename the file to something short, it attaches fine.

I think there should at least be an error message explaining why the attachment was not added, and the '+' column not incremented.

Alternatively it should handle longer filenames.