Last week I posted about a bug in the Xpages File Download Control.
See the post from 27 januari for details.
We have reported the problem through a PMR with IBM, but that unfortunately only resulted in a response that the problem is resolved in 8.5.1. and it will not be fixed in the 8.5.0 release.
In the PMR response IBM did mention a possible workaround could be found in John Mackey's blogpost and a response to last weeks post from Irina Kojevnikova also pointed to John Mackey's post. And as it turns out John based his code on Irina's initial solution.
In that post the solution to the problem is overriding the file download code with custom code to build the old style url for downloading attachments.
On 8.5.0 Domino the subdirectory is omitted in the file download control, so another work around would be to place replica of the database in the domino data root directory (nightmare for admins).
But John and Irina's solution is cleaner.