I was on level 3 in the original when it happened, specifically when you open the door which you unlock with the key you get when you've activated a terminal, the door which is here:
The first level where you encounter the "trespasser" guys with a grenade launcher and a minigun.
It happens on level 2 of mission pack Zaero as well.
It seems to happen any time some sort of transition trigger is activated, like opening a locked door or approaching the exit of a level.
This is the original game's behavior. Might as well be an intended design choice by Quake 2 team to emphasize certain events - either way not something that needs actual fixing.
I was on level 3 in the original when it happened, specifically when you open the door which you unlock with the key you get when you've activated a terminal, the door which is here:
The first level where you encounter the "trespasser" guys with a grenade launcher and a minigun.
It happens on level 2 of mission pack Zaero as well.
It seems to happen any time some sort of transition trigger is activated, like opening a locked door or approaching the exit of a level.