Dear Luna Wu,
it is very hard to tell what the problem is, but it's most likely not related to rpg_dvs_ros driver or the cameras. It seems there is just no data recorded in the second file.
It is impossible to tell what happened with the information you provided, to be able to assist, please describe the procedure for the recordings, with exact rosbag command lines you used and roslaunch files. Make sure ROS topic names are matching while recording.
Best regards,
Rokas