AW3225QF fade/flicker issue in dark scenes when using SDR.

I just bought an Alienware 3225QF OLED monitor, and I'm seeing an annoying flickering issue when viewing dark scenes in SDR mode.

Basically, what happen is when there's a dark scene with no motion, the dark areas slowly fade out to almost complete blackness.  Then, once movement starts again, they snap back into visibility, making a very jarring flicker effect, especially around the edges of the darkest part of the scene.

It's extremely noticeable when playing a dark game, standing still in a dark area, and looking at a dark wall for a moment before shifting the view slightly.

The easiest way I've been able to reproduce this is in an old game with lots of dark areas (I've been using Thief 2: The Metal Age), but it also seems to happen in dark films (especially when pausing/unpausing), and in other dark games.

These seems like there's a fault with my monitor, as surely the blacks aren't supposed to flicker like this?

The issue doesn't seem to happen when HDR is enabled (though that obviously has its own problems when trying to run SDR content.)