I’m not sure I agree that it’s a good idea to instruct users to install an independent fork of MRtrix3’s development branch, to diagnose a problem on our main release branch. Besides, the code you’re referring to is already available on our repository and accessible with a simple git checkout dev.
Users should note that the 3Tissue repo essentially provides the entire contents of our development (dev) branch – which we ourselves haven’t released yet – with the addition of the ss3t_csd_beta script to perform single-shell 3-tissue CSD. We don’t consider that version of the MRtrix3 code as suitable for deployment yet. Furthermore, issues with the 3Tissue repo should really be addressed to the appropriate forum, according to the 3Tissue documentation itself – not the main MRtrix3 forum. It is an independent project, not officially affiliated to the MRtrix3 project, or endorsed by its development team.