Judging from your problem, I would assume ACP isn't causing this, but likely another equipment mod, or a glitch in Elemental itself (hey, it's possible, right? 
).
I use the most recent version of ACP, among others, and haven't noticed exactly what you're talking about (all defense values for items are showing up just fine for me), however I have noticed something similar:
I've encountered a glitch (just recently) where my sovereign could not equip any new shoes/boots of any kind (all other parts seemed to equip perfectly); the shoes wouldn't show up at all when trying to equip them, but he clearly had them whenever I attempted to trade them between other people. Also anyone else I tried equipping shoes on worked perfectly.
I use about 5-6 mods (all well-known on this forum), and a couple of them add a large amount of extra selectable equipment during sovereign creation (should narrow that down to 1 or two mods). My sovereign was wearing boots from one of these mods which were equipped during sovereign creation, and I could not un-equip these boots no matter what I tried throughout the rest of the game. Hope this helped you at least slightly.
