I have used my own c3d data to perform human gait analysis in mocap model. And it has a wrong initial postion so that it can’t run kinematic analysis. And when I checked this with default c3d data, the same errors are observed there also.
Please try to change the initial position in the trialspecific.any file, so that the model loads cloaser to the recorded markers.
If the model fails in the first time frame it can be the initial position which are not good enough but it can also be related to the marker configuration, so please verify the markers are placed correctly.
Please have a look at this wiki page: