Fmriprep: Visual Report discrepancy to .nii images

Hi all,

while checking visual reports (fMRIPrep version: 20.1.1) for one subject, we encountered some strange plotting / distortions / alterations / gradients in the SDC Figure:

or here:

I visually checked raw data, bold_ref.nii and the preprocessed .nii (also im comparison to a “normal” run of this subject) and did not find any evidence what might have caused this. I furthermore checked intensity values before and after fmriprep as well as signal timeseries without noticing any abnormality.
So, IMO the (raw, prepoc) data looks good … but to doublecheck: does this looks familiar to someone (maybe @oesteban)?

Thanks in advance,