The constraint described above involves many degrees of freedom. The internal constraint elimination algorithm will have to solve a large system of equations, which may lead to excessive memory usage or inaccuracies. Sometimes due to inaccurate handing of the constraints you may observe convergence issues in the model. If this happens, select the Use weak constraints checkbox (enabled by Advanced Physics Options) to use the weak form of the constraint. The Lagrange multiplier, <phys>.<feat>.th1_lm, for this constraint provides the reaction torque on the cross section.