I have confirmed that the Copy button does not copy the text correctly, and we are looking into a fix for that. In the meantime, you are still able to highlight the text with your mouse and either right click to copy, or use "ctrl+v" to copy.
However, the Copy button does not seem to be breaking the page in way, it simply does not copy the text. Could you describe in more detail what is happening?
It may also help to know that you normally have to click on the OK button for the dialog box with the URL to go away, and to go back to the file manager.