I had to retype to this entire post because I was upset the first time.
During the final encounter with Fabius Bile, the final boss of the Prophecy campaign, I went to gather the loot off the floor after beating him. Suddenly, after only grabbing a single item, the final cut scene for the game started. Do it starting early, i was not able to get any of the reward for beating him.
I'm not sure what triggered the cutscene, but it was something I didn't notice, or perhaps it was forced. Perhaps a prompt can come up asking if I'm ready to leave, or I can interact with an object to leave the stage?
Admittedly, I feel a bit sore about losing out on all that cool stuff. :c