I think I've found some things about items drops.
1) It seems that only some battle formations can drop items, and when they do, it's always the same item.
2) I tweaked the game so that when a battle formation can give an item, it always does. I also tweaked the game so that every ennemy miss their attacks, and so that the damages you make are huge.
3) There's a bug in the routine displaying battle stats : it doesn't compute well the position of the item dropped, so you can't see the item name. On the picture below, the item name should be in the red box :
Here's a patched SLPM file with the tweaks described in 2. Replace yours in the ISO with this one (make a copy before). If the crashes are related to items drops, this ISO should crash much more frequently. If this is the case, I've good reasons to think that fixing 3 would fix the crashes.
Link to the patched zipped SLPM file :
http://we.tl/RrLP11mXbNPlease report your crahes