UI lag when HDR is enabled

I am experiencing massive, absolutely staggering Menu/UI lag when HDR is enabled. There's severe frame pauses every time I move the cursor (and only when I move the cursor?...). It is strictly in the interface elements/weapon overlays. In-game combat, moving, interacting is all smooth and flawless.

I have a triple monitor setup with MELE on a 4k@120 with HDR enabled, driven by a 1080 TI and an i9. I've attached the dxdiag. 

I'm playing with borderless window mode, though fullscreen/windowed have no effect. V-Sync is disabled in-game, but forced-on in NVIDIA control panel, and frame rate is capped at 120 FPS.

I've tried a number of things:

1. Disabling Origin/Steam overlays has no effect.

2. Disabling/removing auxiliary/game controllers has no effect.

I'm just baffled that it works absolutely fine if I turn HDR off. I would like to play with HDR, it looks gorgeous, but the UI lag is terrible.

Edit: This had been for ME1, but a quick test of ME2 and ME3 confirms the issue is present for those games as well.