Notifications on Oreo+ no longer have the ability to set custom sounds and vibration patterns.

[blockda]

Or it is a samsung phone thing. Discovered this on the Note 9.

[Ruagh]

Xiaomi Redmi Note 5 - notifications arent working in most builds, although vibro works in beta 7. Toast messages are disappearing just like timers, my guess its just a read or write config error.