You might want to turn the two surface meshes in Hex_Screw.obj and HexBitEE.obj into tetrahedral-mesh VTK files following this Google Doc Advice to prepare non-convex meshes for hydroelastics. Passing OBJ files as compliant-hydroelastic collision geometries means we will use their convex hulls (https://drake.mit.edu/doxygen_cxx/group__geometry__file__formats.html).

The tools mentioned in the Google Doc should work if the obj files have water-tight surface meshes. Otherwise, you could send me the obj files, and I can help make them into tetrahedral-mesh VTK files.

The tutorial https://github.com/RobotLocomotion/drake/blob/master/tutorials/hydroelastic_contact_nonconvex_mesh.ipynb uses tetrahedral meshes in VTK files for collision geometries.