Notifications that arrive on some phones and not others
Nearly always aggressive battery management by a manufacturer. The fix is architectural rather than a setting.
Android's hard part is variety. Screen sizes, OS versions, manufacturer skins, and background execution limits that differ by vendor all mean an app that runs perfectly on one phone can misbehave on another in ways nobody predicted from a simulator.
So testing runs on real devices across a spread of versions, and background work is built against the strictest battery rules rather than the most permissive. Notifications that arrive on one manufacturer's phone and vanish on another are almost always this.
We build in Kotlin with Jetpack Compose for native work, and React Native where the same product ships to both stores. Play Store release management, staged rollouts, and Play Console policy handling are part of the work rather than a handover problem.
Nearly always aggressive battery management by a manufacturer. The fix is architectural rather than a setting.
A device and version matrix, tested properly, turns a stream of one-star reviews into a short list of specific bugs.
Managed deployment, kiosk mode, and offline capture for staff who are not on the app store at all.

Discovery calls are free and usually last 30 minutes. We listen first, and we will tell you honestly if android development is the wrong thing to spend money on.