I've moved my users-folder (C:\users...\documents) to a network location.
as soon as this is the case, I cannot install OpenNumismat.
The setup will fail with the error:
"Internal error: Failed to expand shell folder constant 'userdocs'"
As soon as I restore the default location, the setup is working - and then, I can move the users-folder back to it's network location.
But then, of course, the Software can't find the path where the DB file was stored, and I have to open the file manually from it's 'new' location.

Based on some research I did, it is likely related to the usage of {userdocs} in /tools/setup.iss
[Dirs]
Name: "{userdocs}\OpenNumismat"
Name: "{userdocs}\OpenNumismat\backup"
Name: "{userdocs}\OpenNumismat\templates"
This should probably be something like:
[Dirs]
Name: "{userappdata}\OpenNumismat"
Name: "{userappdata}\OpenNumismat\backup"
Name: "{userappdata}\OpenNumismat\templates"
Source:
https://github.com/docker-archive/toolbox/pull/441/files