The error is likely because you have a tetrahedron in the mesh that is very very thin. DMM can handle inverted tets that happen during simulation robustly, but it can have issue with tets that are inverted upon startup.
I would suggest that you run meshverify on your object prior to turning it into DMM to see if there are any highlighted areas with very thin tets. Assuming that is OK, it is possible that netgen has created a bad inner tet. You can adjust that by slightly varying the