If markers are incorrectly tracked, problems may arise in skeletal data. For instance, if a hip marker is not tracked properly, that can affect not just the hip motion but also the entire body motion. If a shoulder marker is missing, that can severely change the motion of the arm attached to the shoulder. When such problems happen, you have to either try to retrack the motion in post-processing or try to edit the motion, which is both difficult and time consuming. Pay attention to the outputs of skeletal systems and know what types of tools are available to deal with issues in data.