just ran the spider caves in tindirin. and just opened slots on my Grimm to use Nightshade happiness and Kelvin aa for bosses.

I tried timing the stun multiple times so the boss wasn't movement for more efficient testing and kelvins stun wasn't working.

I ran on this map to test the stun and also ran easy brackenridge maps to test. will try to post videos soon.

I have been away from the game for sometime and was wondering if it's bugging due to it being a recent update or if kelvins stun was nerfed to not be 100% efficient.
pretty sure George is 100% efficient so I will give him a try next but I prefer the bleed effect with kelvin on bosses.

Anyone else having this issue with other pets? Or can confirm/deny kelvin stuns being 100% still?