that sounds like a deeply frustrating issue when your app doesn't just fail but seemingly triggers a system-wide VoIP deadlock affecting other apps like WhatsApp and requiring a device restart! This strongly suggests a significant interaction problem likely stemming from how your app utilizes PushKit and CallKit, impacting core iOS communication services – a very different layer of complexity compared to managing backend network infrastructure often seen in the Wholesale Voip ecosystem. To pinpoint the cause, meticulously review your CallKit lifecycle management, ensuring every call state and ending (especially errors) is correctly reported and audio sessions are properly managed; use Xcode's Instruments to hunt for resource leaks (memory, sockets, audio resources) or performance bottlenecks; scrutinize your PushKit payload handling and background task execution for efficiency and potential hangs; investigate internal concurrency issues or deadlocks within your call logic; and use Xcode's Console to monitor system logs for relevant messages from related OS processes around the time the deadlock occurs, noting any correlation with specific iOS versions. Detailed logging and perhaps attempting to reproduce the failure in a minimal test case might also be key to isolating this challenging system-level problem.