We have acknowledged this issue and could reproduce it, though it is still on-going and not fixed yet.
The display sometimes ‘flickers’ (on usage or when going to sleep) when the brightness level is set on minimum.
It can happen with both the Adaptive brightness on (then in a dark environment) and off (if the brightness level is set on minimum).
It is mostly noticeable in a dark environment.
The current workaround is to set the brightness level to a higher than minimum level.
Please report here if you still experience flickering.