I have the same problem on my S9. When I arranged a technical support session in Apple Store, the genius told me it was because S9 is too old to upgrade to 26.0.2 and suggested me to trade-in a S11. I followed his advice and got a new S11. However, the problem persisted. I did all you did but still can’t fix the problem with the new S11. So I returned the S11 to Apple Store for refund. Unfortunately I couldn’t get my old S9 back but only the refund amount.
Before I return the watch to Apple Store, I downloaded all logs and put them to AI which gave me the following findings:
1. Extreme Memory Pressure and Thrashing:
The `stacks-2025-11-02-182624.ips` log reveals critically high memory pressure. The system recorded **2.6 million page compressions** and **1.7 million decompressions**, with only **798 free memory pages** (approximately 12MB). This indicates that the CPU was constantly engaged in memory management, preventing it from entering low-power states and leading to substantial power consumption.
2. Widespread System Application Crashes:
* The `ExcUserFault_NanoSettings` logs show repeated crashes of the core `NanoSettings` application. The exception type is `EXC_GUARD` with a `WEBKIT` termination namespace, suggesting issues with resource access (e.g., Mach ports) likely related to embedded web content within the Settings app.
* The `Diagnostic-3743` log indicates a crash of an internal diagnostic tool itself, with an `EXC_BAD_ACCESS` (segmentation fault) at an invalid memory address. This points to deeper system-level memory corruption or fundamental software defects.
* Frequent crashes and subsequent restarts of these system components demand additional CPU cycles and resources, contributing to battery drain.
3. Core OS Instability (CoreMotion Database Inconsistency):
* The `stacks-2025-11-02-182624.ips` log explicitly states a `reason: "Potential CM database inconsistency, time jump"`. CoreMotion (CM) is critical for processing sensor data related to activity and health. An inconsistency in its database can lead to:
* Excessive sensor polling or processing as the system tries to correct the data.
* Increased CPU utilization for reconciliation efforts.
* General system health degradation, impacting overall efficiency.
4. Inefficient Inter-Device Communication:
* The `Bridge-Pair-Performance-Report` highlights significant delays in communication between the Apple Watch and its paired iPhone. The "Longest Local RTT Measurement" was **5.78 seconds** for `PBBCMessageIDSendProxyActivation`, and the "Average Local RTT" was **1.18 seconds**. These high round-trip times indicate that the device's radios and CPU are working harder and longer to maintain connectivity, leading to increased power consumption.
5. Problematic Software Update Process:
* The `OTAUpdate-2025-11-02-19-14-46.ips` log indicates a failure or significant delay in an Over-The-Air (OTA) software update process, specifically stating: "Update finish took too long since apply finish event" (error 78). A stalled or problematic update can cause background processes to continuously attempt completion or recovery, preventing the device from entering low-power states and consuming substantial battery.
These findings suggested that the severe battery drain on my Apple Watch S9 and S11 was not due to a single misbehaving application, but rather a combination of systemic issues including severe memory pressure, critical system component crashes, core OS data inconsistencies, inefficient communication, and a problematic software update state. This creates an environment where the device's CPU, memory, and radios are constantly active and operating inefficiently.
I hope this detailed information proves valuable for your problem. Since I have returned the new S11, I can wait until Apple fix the problem before I get another new S11.
