Rebex is not retrieving image files with %20 (space) in the name. Example:
09:14:18.453 Request(242): GET /img/MM/Warhorse.png (client: [::1]:52049)
09:14:18.464 Request(242): Sending response: 200 OK (file: /img/MM/Warhorse.png; type: image/png)
09:14:24.583 Request(243): GET /img/MM/Warhorse%20Skeleton.png (client: [::1]:52055)
09:14:24.590 Request(243): Sending response: 404 Not Found (file: C:\Apps\Rebex\wwwroot\img\MM\Warhorse%20Skeleton.png)
Both of these files are verified as existing.
Installed Microsoft Windows IIS (default optional feature) on Windows 10 and the response happens as expected - each file is retrieved for each respective call.