Lens Flare size popping

My lens flare is tied to something else in my scene, so I have this in Update():

 if (Game.isPlaying && !isFlickering && !fadingOut)
 {
    flare.brightness = otherThing * modifier;
 }

But sometimes I need the flare to flicker for a minute, then go back to matching otherThing in Update. So I set isFlickering to true and then Lerp flare.brightness up and down in a coroutine. When the flickering is done, I smoothly transition from the current value back to otherThing X modifier using another coroutine. Once the Lerp back to otherThing X modifier is complete, I set isFlickering to false so that Update will take over again.

.

This works great, but there's a small pop in the moment where Update takes over again. It looks like the flare gets bigger but doesn't change brightness. I've tried logging flare.brightness at various stages to see if the value itself jumps, but it doesn't. I think it might be something with the Unity flare component.

Has anyone seen something similar?