I'm not sure what file or directory the error message is referring to, nor what the meaning of nfaces is. I am running version 6.0 on macOS Mojave. I have also attached a truncated version of the ascii file for inspection purposes (the whole thing was too big), which was converted from a csv that was generated by a python script correcting for site effects. This script took in as input the original ascii converted from the original lh.thickness file using mris_convert. The coordinates correspond to the fsaverage template (~160k vertices in the whole file).

Thanks in advance for any guidance,