[Python][Rosbag] Written rosbag has same start and end dates - All topics are published at the end

Hello everyone, I've been running around code APIs, forums and other wells of knowledge but I can't find the solution to my problem. Here's what I want to do: - open a .mat file (Done) - read the structure and fetch the data (Done) - create a rosbag with a topic for each message in the mat file (Fail) I can write to the bag file with for t in range(MESSAGE_SIZE): ros_msg.data = MESSAGE[t] t_msg.secs = t_vec.sec t_msg.nsecs = t_vec.nsec bag.write("/topic", ros_msg, t_msg) Where t_vec is an array, filled with timestamps of said messages. It's under the same format as the ROS time. Execution of the code is done smoothly. However, when I try to replay the bag to check what has been written down in it, I got these issues: - rosbag info tells me that bag duration is 0.0s - rosbag info tells me that the start and end date are the same (final value of the time vector used in the bag creation) - when I play the bag, the duration displayed in the terminal is 17s, whereas the time vector is 89 seconds long. - all messages of all topics are published only when the bag reaches its end. - the /clock topic is well published and its time is correct. I honestly don't know where to look now... Any help would be greatly appreciated. Thanks in advance!