Freesurfer - Problem averaging surfaces

Hey all!!

I am currently running surface-based analysis and I am trying to average the surface of all my subjects using the following:

make_average_subject --out avgsubject --subjects sub-003/sub-3 sub-004/sub-4 sub-006/sub-6 (…)

The code runs until a certain point and then presents the error:
Reading source surface reg /…/sub-003/sub-3/surf/lh.sphere.reg
Loading source data
ERROR: could not read /…/avgsubject/label/tmpdir.annot2std.26750/seg.1.sub-003/sub-3.mgh as type 3
ERROR: make_average_surface

I couldn’t find what this “type 3” could potentially be and the file that it was supposed to be read doesn’t exist and/or was not created.

Has anyone ever encountered such an error? Or does anyone have another suggestion of how to average surfaces?

Thanks in advance