fsck can fail at any stage, it can be due to some file were not properly written as most of the latest filesystems including photon os is journaling filesystems. If the filesystem is attempting to write and could not complete it then the journal would have been corrupted.
Most of the VCSA partitions are lvms, if the lvms did not mount properly by the time fsck started to correct the corruptions can also lead to this.
In general, linux machines are sensitive to storage/power outages. When you fail with fsck, run the journalctl which can give you more info on which partition it failed. May be by tracking that partition, we may try to track back the issue what would have happened on that disk
Thanks,
MS