Whenever you are in a period of stagger, Psyker’s ult will not stagger enemies. In the above video, I am hit by a ranged attack while sprinting, staggering me. During this period of stagger, I fire my ult, and it does not work.
Steps to Reproduce:
Go into the meatgrinder and spawn an enemy (ranged or melee). Immediately after getting hit, fire your ultimate into the enemy. It does not happen consistently, but I only observe it occurring after I get hit.
If I let myself simply get shot without taking HP damage or from being staggered out of a sprint, then my ult still works consistently.