[Freesurfer] Some volumes not loading (corrupted?)

Hi all,

After doing some manual edits to the wm and pial masks, I recently had a recon fail with the following error:

mghRead(/subject_177/mri/brainmask.mgz, -1): read error

Invalid argument

mri_em_register: could not open mask volume brainmask.mgz.

When trying to load either the brainmask.mgz or wm.mgz into freeview, these also fail, e.g.:

mghRead(/subject_177/mri/brainmask.mgz, -1): read error

MRIread failed: Unable to read from /subject_177/mri/brainmask.mgz

All other volumes load fine.

Can you think of what I might have done to corrupt these volumes? And is there a way to revert to the most recent version, so that I don't lose previous edits?

Thanks so much, Rachel