Hi and welcome to Neurostars!
I have a few questions that might help with this.
- What version of QSIPrep are you using? If not most recent (0.16.1 at this time) can you try updating?
- Is there anything that might differentiate these 5 subjects from the remaining subjects?
- Are your data BIDS-valid?
- Does the error persist after retrying with a clean working directory?
Best,
Steven