Hi @edelaire
I have no experience using FreeView, but I guess some fields in the data (Transformation matrixes/headers, variables names ...) that are exported from Brainstorm are invisible or can't be read from FreeView.
It needs further investigation, and it may take some time from our side to get to this issue.
this is a good path to investigate, so we can compare the data structure in both files and check what are the differences.