Inverse Dynamic Failure: singular KTT matrix

Hi,

I am working on an modified AMMR model, aiming at mimicking a karate standing-straight punch. I have added 5 simple driver to drive the shoulder, arm and pelvis and the kinematic study is run as expected. But when running the inverse dynamic study, the programme gives a warning as below:
ERROR(OBJ.MCH.MUS4) : //d..k/s..t/s..1/m..x/A..y/p..w/p..1/project1.main.any(48) : Study.InverseDynamics : Muscle recruitment solver : solver aborted due to singular KKT matrix

Could anybody help me to find where the problem lays? Thanks a lot and please reply as soon as possible - I need the solution urgently for my report.
project - new.zip (239.2 KB)