Thanks for the example files.
I added a basic support for reading these files in Brainstorm. Update Brainstorm and you shouldn’t get this error anymore.
However, I couldn’t find some of the information present in the g.tec Matlab exports: the epoch separation, the marker names and latencies… If you need to read additional information from these files, I would need your help exploring the structure of these files further. You can place a breakpoint in this function, and try to get the information you need.