Had a really annoying issue thats really particular, but i've found a solution, so here goes for anyone watching HDR content on netflix with subs.
Basically, subs on netflix are rendered at peak brightness, for visibility. This means the sub portion of the screen has to be lit up by the edge lighting inherent in the KS8000. Having smart LED set to high (or low) since you're watching HDR and want to get the most out of the standard, will make dark(ish) scenes bloom whenever the subs are on-screen, leading to a noticable brigtness change near the top of the screen, due to edge lighting. Once you notice this, it gets to be infuriating, as it almost acts like an eco-sensor on molly, becuase the subs usually arent displayed constantly.
A reference scene - second episode of Iron fist, 35:00 in, Danny is lying in bed talking to a dude. Really noticable.
You've got 3 choices to limit this, 2 of them sub-par:
1): Watch without subs, which won't be viable for everyone
2): disable SMART LED, which kinda makes HDR content moot,
OR
3): Customize your subs via netflix.com under account, and make them semi-transparent. Then reload the netflix app to make the subs refresh. White subs will appear more like a muted light grey, and the peak brightness of these should not noticably lead to blooming when there's subs in darker scenes.
I've no idea if this happens on UHD content or if its netflix-exclusive, since i dont have a UHD player, but its such a relief to have found a fix.