I am sorry about this problem, we are able to replicate it.
The issue is that the interpolation functions used for the markers has some end effects due to filtering.
This introduce some artificial acceleration in the last frames which means the model is not able to create balance using the foot contact forces.
To fix this subtract some frames from the analysis.
- in the file TrialSpecificData_GRFPrediction.any
- add this line LastFrame = .C3DFileData.Header.LastFrameNo-3;
Hopefully this will resolve the problem.