Dear Nina,
In case the Dicom files can't be retrieved and the scanner protocol is not available (or if this is very difficult) you could give a try and look at the raw Dicom-imported niftis. Possibly there are subjects with fast head motion, which can be detected e.g. with Artrepair. If the subjects move during the acquisition of a volume you have relatively good chances that e.g. only the second "part" of the slices is shifted spatially, and when compared to the previous volume you can then infer the acquisition order easily based on the movie/slider option in Artrepair.
Of course, ideally there is no fast head motion at all, but depending on population / number of subjects / length of experiment at least a few volumes of the whole study might be affected anyway, and this would be sufficient then.
Best
Helmut
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