We didn't change anything, but the printer started "Paper jam" at the end of printing. The bottom of paper, about 2",  doesn't go through the printer, and the error sign light becomes red. When I press the power off button and turn it on again, the stuck paper comes out smoothly with the 2nd paper which comes out smoothly, too. This paper jam occurs each time when I print something. Does anyone know how to fix this problem?