I have roughly determined that the problem was caused by an overly high version of the graphics driver. I reverted the computer's driver to version 576.88, and then there were no any stutters. I have saved this information here, which will also help you have an impression to deal with similar situations. Currently, the latest NVIDIA GRD graphics driver will cause severe stutters during the running of games in the Renpy engine, and even if you exit the game, the severe frame drops of the computer cannot be restored. Restarting the computer will restore it.