Hi Jan, Thanks for your post, the additional environment details, and screenshot. Would you kindly point me to the repository with the "block" directory (e.g., https://simtk.org/svn/opensim-matlab) where you checked out the source code files? This helpful information may lead to identifying the root...

You could modify the model file, but it would be much easier to simply "lock" the dofs (i.e., coordinates) that you no longer need. You can lock coordinates in the Coordinates window.

<t>Hi Kathleen,<br/> <br/> You are not the first (or the last) to experience this problem. Inverse kinematics although simple mathematically is much more difficult in practice. <br/> <br/> You may notice that the RMS marker errors are high (greater than a few cm) during inverse kinematics. This sugg...