Mask Scent 4 (Source)

guess my answer will be different. I hunt a lot, and I prefer to hunt big creatures. My maskscent brakes only 50% of the time for regular Kimos (lvl 90). It also brakes only at about 70% at juvenile krayts, but it will always brake at any other types of krayts. Also, for the reference, it has about 20-30% chance to brake for ancient bull rancors (lvl 95). My guess is that it's somehow related to the level of the creatures you can trap. I'm a master ranger and I can trap kimos, juvenal krayts and ancient bull rancors with almost no problem, but my traps will never work on anything over lvl 120 no matter how many time I'm going to throw them. Same thing with maskscent. I can't hide from anything over lvl 120 (not that it's that easy to find agro creatures over lvl 120, but giant dune kimos and krayts brake my maskscent every time).