Screenshots made in dynamo using the camera on a 4K screen will not be readable.
The same goes for selecting nodes to put on the canvas, my mouse pointer has to be under the node to select the correct one.
PS i should upload this to Github i know.
Rather late to the party, but this actually works as intended : the problem you have is that you are too zoomed out in the canvas. Try zooming in further and then use camera button (top-right) built into Dynamo - it screenshots the entire canvas, not just the visible portion.
It also works on a 4K screen, at least on my hiDPI Surface Book.