How to track the distance that cells travel using Icy?

I have a video with moving cells and my goal is to receive speed of each cell. So, first I use Spot Detector and then Track Manager to measure distance that cells travel, but for some reason program splits the trajectory of one cell into several fragments and considers that this is not the movement of one cell for a certain time, but the sequential movement of several cells.

On this image you can see the trajectories not as lines, but as set of points. Maybe I use wrong parameters for tracking but I’m new to use Icy so I’ll be grateful for any suggestions.