At one point, Valve accidentally broke blinking in HL2 era versions of the Source engine.

Like uh, there was originally, for all humanoid NPCs with visible eyes, some kind of timer and functionality that would cause NPCs to blink, at semi-random, semi-regular intervals.

Somewhere around approximately 2010-12… they broke this, and no NPCs would or could blink anymore.

… Last I checked, roughly a decade later… they appear to have fixed it.

But I remember this being broken for like, years.