When you finish a line, the test program tries to see if what you typed corresponds to the top line in the test text window. If the test program can't find a good enough match between what you typed and the top line, the test text window won't be scrolled up one line.
If this happens, you should either backspace over what you have typed and try to get back in synch with the test program, or just type the top line visible in the test text window from the start of the line.
