Can't get field parchment to work

I've successfully completed the Skahnowa Chapter 7 Field Parchment several times (gearing for 75 content), with different items, and didn't manage to get any augment on any of them. I did it with Black Ribbon, Jeweled Collar, and Scouter's Rope, the latter of which I confirmed has apparently worked for others according to notes on the wiki. Each time I traded 1500 gil, 30 Beastmen's Seals, and the piece of gear. The Scouter's Rope I made sure to remove from any gear swaps and kept untouched in my inventory. I got a chest each time and only got experience points, with no change to the equipment.

Any ideas on what's might be going wrong here would be appreciated.