Check for different qform/sform matrices in multiband/sbref pairs #2367
Description
When fmriprep processes multiband data, it appears to rely on the sform matrix of the sbref, and makes the assumption that the sbref's sform matrix is the same as the multiband's sform. If these are not the same, fmriprep completes processing without error, but all the transformations applied to the multiband data are applied assuming a wholly incorrect xform. This leads to bad registration and normalization of the multiband images.
Now, admittedly, this is likely not a problem most folks are going to encounter, as current multiband protocols spit out correctly aligned image pairs. This issue happened with the data I was working on, because the multiband data was collected before official protocols were released for the scanner, so the image files were reconstructed using some custom scripts. These scripts put the correct xform matrix in the qform slot of the multiband, but put a different, and incorrect, xform in the sform slot of the multiband.
It would be useful if a check was implemented to just make sure that any multiband data has the same sform matrix as its corresponding sbref. No need to fix the issue in the pipeline, just throw an error if they don't match.