Imagine you have created a movement as on the image below (filtering traffic objects crossing line2 and then zone1 in that order). The trajectory of the traffic object A ends within a zone1 and does not leave the zone. Therefore, the exit time of the traffic object A is missing in the report as well as the travel time is set to 0. Why is that? As you can see, not all trajectories in the exit zone1 are ending in the same spot. We protect you from getting inaccurate information about the travel time.
Example where the traffic movement is not defined ideally
Now the quick trick that will fix this issue for you: by using line as the exit area instead of a zone you are measuring the exit time as the exact intrusion over the exit line. See the image below. In this case, all trajectories crosses the line1 and therefore, the exit time of the traffic objects is determined and it won't be missing in the report as well as the travel time.
Example with the traffic movement defined correctly