Version used: 1.4.0-alpha01
Devices/Android versions reproduced on: pretty much any device and api (seen on emulators/Huawei/Samsungs, api 27/29/30)

If you have a stack of activities with android:configChanges="uiMode" and you call AppCompatDelegate.setDefaultNightMode it can cause other activities resources (1 or more) not to be updated (and onNightModeChanged not triggered).
It happens when the setDefaultNightMode is called from another thread that the top activity (with a handler Handler(Looper.getMainLooper()).post {} or RX AndroidSchedulers.mainThread().scheduleDirect {})

Eg :
Activity A with uiMode
Activity B with uiMode
Activity C with uiMode

Here is your stack : A > B > C (C on top)
Call AppCompatDelegate.setDefaultNightMode with a new mode on activity C (but not directly from this activity, ex with RX AndroidSchedulers.mainThread or an handler)
Activity C receives the onConfigurationChanged/onNightModeChanged, Activity B receives the onNightModeChanged but one time out of two activity A not receives the onNightModeChanged (and the resources are indeed not updated when back to A).

Process:
A > B > C > setDefaultNightMode OK > go back to A (B & C destroyed) > B > C > setDefaultNightMode KO (wrong configuration for A)
& so on (OK/KO/OK/KO...)

I think the fix for the issue 169770885 leads to this issue.
Before the fix of the 169770885, i had a different issue (since 1.2.0) (onConfigurationChanged not called on Activity C after setDefaultNightMode)

Technically here is what I have seen :
- The AppCompatDelegate has 3 AppCompatDelegateImpl (for A,B and C) in sActivityDelegates (both when the setDefaultNightMode works well or not)
- When calculating the currentNightMode in AppCompatDelegateImpl.updateForNightMode, the Activity A has the wrong value so the changed is not applied

Regards,