If Wèi Jì has appeared in your reading, the book is naming the configuration with which the entire sequence ends — and the configuration is incomplete. Every line of the hexagram is in the wrong place: yang in even positions, yin in odd ones. The opposite of Jì Jì in every detail. The book closes its sixty-four-hexagram sequence not with completion but with the crossing not yet made.
Classical commentary reads this final placement as deliberate and central to the book's whole teaching. The text refuses to end with arrival. The little fox in the judgment image has crossed almost all of the frozen river; at the very end, the tail dips into the water. The crossing was almost finished. The book leaves the reader at this almost. The configuration is forward-looking, not closed.
What the book counsels is the patient, careful work of bringing each element into its right place. The image's instruction — 慎辨物居方 — careful discrimination, things placed in their proper positions — is the technical description of what unfinished business looks like when it is being handled well. The reader is being asked to attend to the details of the last yard, on the understanding that the fox who hurries at this point is the fox who wets the tail.
Wèi Jì's failure mode is the rushed final move. The book's last word is, characteristically, a warning. The hexagram appears when the reader is near the end of something important and the temptation is to skip the careful sorting of the last details. The book's whole sequence has been preparing the reader for this. Completion is rare, fragile, and easily missed at the last step. The wise close of any cycle is also the patient setup of the next one.