Hello FreeSurfer Developers,

I attempted to run recon-all in cerebellum hypo case, but it resulted in an error.

The message indicated “trgvtxno = -1 < 0.”

When I inspected the data in Freeview, I noticed that the left and right white matter and pial surfaces were intersecting near the corpus callosum.

Therefore, I mannually removed the white matter around the corpus callosum in wm.mgz and reran  recon-all -autorecon2-wm -autorecon3 -subjid <subject>.

However, the same error continues to occur, and left and right surface isn't separated.

(https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/TopologicalDefectV6.0)

I've searched the list and no similar errors have been reported. 

Does anyone have any thoughts on how to trouble-shoot this one? 

Also, Ive attached the recon-all.log in case it's of any use. 

1) FreeSurfer version: freesurfer-macOS-darwin_x86_64-8.1.0-20250718-f30dfed

2) Platform: macOS Tahoe Version 26.1

3) uname -a: Darwin RELMPEDFAC27837 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:26:51 PDT 2025; root:xnu-12377.41.6~2/RELEASE_X86_64 x86_64