Yes, this sounds structural to me. Prolaspe, maybe, but it could also be twisting or some other mechanical defect. Scopes don't visualize this stuff. You may need defecography to diagnose it. This is fluoroscopic imaging where the pouch is visualized while you attempt to empty it. It is sort of like a small bowel series, except you are given an enema of thickened contrast. Sometimes they can tack the pouch in place if the trouble is just poor support. But, if you are having twisting or telescoping of the bowel, a pouch redo may be necessary.
For the time being, if you can function reasonably well by just taking the time to stand up and sit back down to more fully empty, that sounds like the better option, as opposed to surgery. I must admit, this happens with me off and on, and it is worse when my pouchitis is very active. I am 20+ years with my j-pouch and it has not progressed. But, I don't have continence issues.
Jan 