Problem with tetrahedral soft bodies

[PolyFlo]

Hello together.

Once more I got a problem with soft bodies.

I build a tetrahedral mesh and loaded it as a soft body into Bullet (with btSoftBodyHelpers::CreateFromTriMesh). This works fine. But when I cut the Mesh everything gets mad.

For the cutting I take the soft body out of the calculation of Bullet. Then the mesh is cut and recalculated. Eventually I initialise a new soft body (with the new coordinates and faces) and put it in Bullet. The first few simulationsteps it works (at least if i keep the time step small) but then Bullet sets all coordinates to infinite and my soft body disappears.

Does anyone knows under what circumstances Bullet sets all coordinates to infinite? Are there any rules that indicates if a tetrahedral mesh is suitable for Bullet? How can I find out what went wrong?

I attach a pic to show how the cut mesh looks like (left a tetrahedral Bullet soft body, right a Non-Bullet Mesh after Cut[same size, even the cut woud be similar]).