>_ blog
Bearly Fit: The iOS Crash Hunt
How a missing line of code broke the app on every iPhone launch - and the collaborative debugging that found it.
February 28, 2026 · Debugging · iOS / React Native
>_The crash
I spotted Bearly Fit on LinkedIn - a React Native fitness tracking app that looked promising. Downloaded it, opened it, and... error. Right on the home screen. The app loaded, but an error blocked the onboarding flow. I couldn't get past it.
The error hit during the automatic backup setup phase of onboarding. iOS was trying to initialize a background service that handles data backup, and the failure blocked the entire flow - impossible to proceed. I wasn't the first to hit it - another user had reported the same issue earlier, but their report was dismissed as a pre-release iOS problem on an iPhone 15.
>_The debugging
When I reported the error, the developer initially thought it might be another device-specific quirk. But my report was different - I was on stock iOS, no beta firmware, no unusual setup. That made it clear this was a real bug, not an edge case.
We started debugging together through DMs. The error was consistent and reproducible, which actually made it easier to track down. The stack trace pointed to react-native-background-fetch - a library that handles background task scheduling on iOS. The module was being called before it was properly initialized.
The irony? This bug had existed since the original 2025 release. It was failing silently the entire time - the background service just never worked on iOS. It only became a blocking error when the developer added better error handling to the onboarding flow. The improved code was stricter about initialization state, and that strictness exposed the underlying problem.
Before (silent failure)
Background fetch never initialized. Automatic backups silently did nothing. No crash, no error, no backup.
After (proper error handling)
New onboarding code tried to configure backup properly. Called BackgroundFetch.configure() - which threw an error because the native module was never set up.
>_The fix
The root cause was a missing initialization line in the iOS native setup. The react-native-background-fetch library requires a specific registration call in AppDelegate - one line that bridges the native iOS background task system to the React Native JavaScript layer. Without it, the JS module has no native counterpart to talk to.
One line. That's it. The library's iOS installation docs clearly state you need this call - it's the classic RTFM moment. The developer summed it up well: the line was right there in the documentation, they just missed it during the initial integration. A reminder that even experienced developers skip installation steps, and that silent failures are worse than loud crashes.
>_Outcome
The fix shipped in Bearly Fit v2.0.1. Beyond the one-line fix, the developer also improved the onboarding error handling - adding soft failures and recovery states so that even if a background service fails to initialize, the app degrades gracefully instead of blocking the user.
1 missing line
Root cause
Same day
Time to fix
v2.0.1
Release
This is the kind of debugging I enjoy most - a clear, reproducible bug that leads you through layers of abstraction to a simple root cause. The fact that it had been silently broken since launch makes it even more interesting. Sometimes the best bugs to find are the ones that were always there, hiding behind silent failures.
Original post on bearly.fit
The developer's own writeup of the v2.0.1 release and the crash fix.