Gameplay - Skarner can't stun Master Yi during HIghlander

Hello, and thank You for reading this. I've made another post earlier about this bug, but no answers were given. However, when i hit master yi with fracture, it doesn't show the crystal venom mark, and so i can't stun him, nor deal him the bonus onhit damage, nor trigger the passive. I'm asking if this was intended, because when olaf uses ragnarok, and i hit him with fracture, the mark shows up, allowing me to deal him the onhit bonus damage, triggering the passive, without stunning him (which is right). To reproduce:

1. Pick skarner vs master yi
2. as master yi: activate highlander
3. as skarner: hit master yi (with highlander triggered) with fracture
4. no mark showing up. thank You for reading this, looking forward to an answer.

Edit: i managed to stun master yi with fracture last game, so it seems fine. sorry for false alarm