Success at last; I removed some sharp edges in my model, remeshed ( -> some very fine local meshes disappeared), could run the CCX solver, and then I got the effective masses in a .dat file. Thanks.
I have to do some studying on the CCX solver, I have never used it.
Your constrained DoFs make sense.
I will try all in the morning.
First some sleep, it is already early in the morning over here (Netherlands).