Mercurius has cursed my copy of Dies Irae.
I'm currently working on splicing together the contents of the Acta Est Fabula and Amantes Amentes versions into one complete edition, and one of the reinserted h-scenes plays properly in the Amantes Amentes engine now...but when it ends it immediately loops back to the beginning. So thanks for gifting me with the curse of 永劫回帰 for this Kasumi ero scene, Mercurius.
Now if you'll excuse me, I need to figure out what's causing this bug and how to fix it.