Hi!
I had the same problem, but I fixed it using FEM mesh and Duneuro, it is faster than conventional methods, there is a BS tutorial:
https://neuroimage.usc.edu/brainstorm/Tutorials/Duneuro?highlight=(fem)
Hope it works!
Regards!
ps: I'm not sure but I think it is not necessary to compute BEM when using default anatomy, maybe that could lead to the outside dipole problem