fMRIPrep not showing white matter boundaries in output html

Hi everyone,

for a few of my subjects, the fMRIPrep output does not show the white/grey matter boundary under " Alignment of functional and anatomical MRI data (volume based)". Under “Brain mask and brain tissue segmentation of the T1w” all boundaries are shown and seem correct. Is this just a weird error in the html or is there something else going on?

Thanks a lot!