For any future users: I had this issue as well, particularly after re-running/trying again several times. What worked for me was to clean out the feat/melodic directory of any fix-related files including the processed files in the mc-directory (the .nii.gz files that are created along the way). Especially this last bit did the trick. @OP: did you solve it eventually? ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1