Interesting. I don’t know at all about GE implementation of the multiband sequence. I just saw this from the CNI Center at Stanford where there are using a GE scanner: " CNI sequences generally acquire calibration data at the beginning of the BOLD acquisitions while GE uses a fast separate calibration sequence to acquire this data. " https://cni.stanford.edu/hyperband-transition) . From what I understand you may be in the second case where the calibration data is only acquire once in a separate scan. Here is another discussion about using SBref scans or dummy scans for preprocessing your data:
Single band reference scan settings
Good luck with your study!