So was there any good focus in the original images that have you worried? Is the lens not capable of making a sharp image, period? Or is the lens making a sharp image, it's just 20/40/375 feet closer/farther than you see on the focusing screen?
From what I hear you saying here, the viewing lens and taking lens are in relatively decent agreement. So this means that you should still be getting a sharp image, relatively close to where you focused on the screen. Yet your original post implied that the images were unsharp all over, with extremely unsharp corners. You'll need to figure this out- is the focus setting and agreement between the viewing and taking lenses off? This is a simple procedure to fix. Or is the taking lens junk? This is a different troubleshooting process.
The difference in focusing ease between the ground glass and the fresnel is typical. Get a brighter target.