regards to a stacking work around. with the recent update you cant unstack individual items from non stackable items unless they are in an NPCs store zone. Just drop whatever non stackable stacks you want to remove items from into the NPCs purchase box and then you can "BUY" back the individual items.
Yes indeed, monsters and npc's dissapeer and dont return. They dont trickle back in. You have to restart and dont use the trainer to see them again. Everytime you use the trainer it goes bam blank again!
I have never enabled Easy Kills Function .... soo thats not the culprit responsible for them disappearing
Edit ! All it takes for characters and mobs npc bosses everyone to disappear is for you to press F1 and enable the trainer... that makes them blink out of exsistance until you restart the game without the trainer