Not sure if a bug or posted, but thought I'd contribute.
When you upgrade your Barn to level 2 or 3, you get a quest. The quest gives you an improved trap. That trap has a 100% success rate while you are on the quest. The quest also yields you the caged beast each time you use it. So, don't hand in the quest, keep using the item on the mobs for the quest to get 100% traps. I did this in Gorgron for my quest and was able to stock up on a fair amount of cages for work orders.
GL