[Freesurfer] error loading volume brainmask.gcut.mgz

Hi Freesurfers, I'm trying to remove some dura which affect my surfaces with the command

recon-all -skullstrip -clean-bm -gcut -subjid

but then I can't use tkmedit to check that. The message I get is:

Error: Loading volume brainmask.gcut.mgz Couldn't read the anatomical volume. Tkmedit couldn't read the volume you specified. This could be because the image format wasn't recognized, or it couldn't find the proper header, or the file(s) were unreadable, or it was the wrong size.

Actually I did check in brainmask.gcut.mgz directory properties, and I saw the size of image is something like 150 KB, instead of 1 MB like is brainmask.mgz.

What is the problem?

Thanks, Claudia