As you can see from the video this unit, the Dregg Stalker does not react to suppression correctly.
The first stream of fire he correctly reacts to it and cowers.
The second stream he ignores it for a moment, begins to react then resets back to his idle animation.
The Third stream he reacts correctly
The Fourth stream he reacts correctly
The Fifth stream no reaction
The Sixth stream he reacts correctly
etc etc etc
He is the ONLY unit in the game that reacts this way