In my two phones with avast mobile with licenses(10, 4 current used, 2 android 2 windows), i configure the app lock of many app, as bank apps, delivery app, aliexpress,wish, info sensible apps, etc.
The proteccion work fine when avast remains enabled, aka uper notification visible(can be used in background).
I configure android 9.0 go to not optimize the app and enable it to run allways, also is enabled as system device protection, antithief enabled with google associated, all permissions of notifications enabled.
In certains situations the avast notifications not remains and go out, in that case the avast app protection lock is missing and all apps are accesibles.
Avast bug?.
In another more old phone using another antivirus(avas is not available for that phone) not happen, the antivirus allways remain with tht notification enabled then always working.