Thank you @tmedani. It was a great help.
I’m looking forward to the release of the new binary.
Aside from that, using the GUI to locate a problematic vertex on the surface and then reposition it seems quite limited (I can't see how to change single vertex on display tab..).
Importing the surface (in this case, mid_15002V?) into the MATLAB Workspace to find the location of that vertex, move it, and then re-checking in the Brainstorm GUI is quite difficult.
However, referring to the answer you posted in another thread, and watching the linked video:
By comparing mid_15002V with cortex_fem and slightly reducing mid_15002V, FEM was successfully calculated on the surface.
I’m not sure if this is a general solution, but I’m posting this in case it helps anyone else experiencing a similar issue. Thank you.