How does the rosbag pause work?

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I am using ROS Kinetic Kame and written a small patch of code, in which I have subscribed to certain topics and have corresponding message handler (callbak method).

I am using some Bag files with the ROSBAG tool. I am also aware that message handlers are take care by ROS's internal thread. When I start playing the Bag files, the message handler is called for appropriate number of times, for eg. at a rate of 1Hz. When I say 'Pause' the Bag playback, the message handler is not called which is fine as there are no topics published. But when I say 'Play' again, the message handler is called massive number of times, for eg. with a rate of 1x20 or 1x30Hz. Can anyone have any idea why such behavior ? Thanks a lot.