One UI 8 Sleep Tracking Broken? The “CZA6” Patch Release Notes and Fix

If your Samsung Galaxy Watch stopped tracking sleep stages, logs blank gaps in overnight data, or fails to record sleep entirely after updating to One UI 8 Watch, you are dealing with a known sensor-hub daemon stall introduced in early Wear OS 6 builds. The issue prevents Samsung Health from processing continuous optical heart rate and accelerometer data during prolonged resting states. Samsung addressed this bug directly in maintenance firmware patch CZA6, which restores the overnight sensor polling pipeline.

Quick Answer

Install the CZA6 maintenance update via the Galaxy Wearable app under Watch settings $\rightarrow$ Watch software update. If the patch is not yet available in your region, reset the Samsung Health sensor permissions on your watch and clear the cache partition to prevent the background sleep tracking service from freezing overnight.

Device & Signal Snapshot

Diagnostic Field	Technical Detail
Affected Devices	Samsung Galaxy Watch 4, 5, 6, 7, 8, and Galaxy Watch Ultra
Operating System	One UI 8 Watch (Wear OS 6 base)
Impacted Feature	Overnight Sleep Tracking, Sleep Stages (REM/Deep/Light), Blood Oxygen ($SpO_2$), Skin Temperature
Bug Mechanism	Sensor Hub HAL (Hardware Abstraction Layer) suspension during deep sleep power states
Target Patch	Firmware build ending in CZA6 (or later maintenance release)
Data Risk Level	Low; previous historical sleep records remain intact in Samsung Health Cloud

What to Do: Step-by-Step Resolution

Follow these steps to apply the official patch or restore the background sensor service:

Step 1: Install CZA6 Update    ──> Check Galaxy Wearable for latest firmware
                 │
                 ▼ (If update not yet available)
Step 2: Reset Sensor Privileges ──> Re-authorize Samsung Health background access
                 │
                 ▼
Step 3: Wipe Cache Partition    ──> Clear corrupted pre-update system cache

Step 1: Check for and Install the CZA6 Firmware Patch

1. Open the Galaxy Wearable app on your connected smartphone.
2. Go to Watch settings $\rightarrow$ Watch software update.
3. Tap Download and install.
4. Check the build number at the bottom of the update description. If the last four characters end in CZA6 (or a subsequent alphabetical sequence), tap Install.
5. Keep your watch on its charger until the installation reaches 100% and reboots.

Step 2: Reset Samsung Health Background Permissions (Workaround)

If the CZA6 update has not yet rolled out to your carrier or region, re-establish sensor service permissions:

1. On your watch, swipe down and tap Settings (Gear icon) $\rightarrow$ Apps $\rightarrow$ Permission manager.
2. Tap Sensors $\rightarrow$ Select Samsung Health.
3. Toggle the permission to Allow only while using the app, wait 5 seconds, then toggle it back to Allow all the time (or ensure Physical activity and Sensors are both set to allowed).
4. Return to Settings $\rightarrow$ Apps $\rightarrow$ App list $\rightarrow$ Samsung Health $\rightarrow$ Tap Force stop, then reopen it.

Step 3: Enable Continuous Advanced Sleep Measurements

1. Open the Samsung Health app directly on your watch.
2. Scroll to the bottom and tap Settings.
3. Under Measurement, verify that Heart rate is set to Measure continuously.
4. Scroll down to Sleep and turn ON both Blood oxygen during sleep and Skin temperature during sleep.

What to Check If That Doesn’t Work

If sleep tracking fails to record after applying the patch and verifying permissions:

1. Wipe the Recovery Cache Partition

Leftover temporary files from the major One UI 8 installation can keep the sensor daemon in an error state:

1. Turn off your Galaxy Watch.
2. Press and hold both the Home (Top) and Back (Bottom) buttons simultaneously until you see “Rebooting…” at the bottom of the screen.
3. Release both buttons, then immediately tap the Home button repeatedly (2–3 times per second) until the Select REBOOT MODE menu appears.
4. Press the Home button to cycle down to Recovery, then press and hold the Home button for 2 seconds to select it.
5. In the Android Recovery menu, use the Back button (or swipe) to highlight Wipe cache partition.
6. Press the Home button to confirm, select Yes, and then select Reboot system now.

  ┌─────────────────────────────────────────────────────────┐
  │ Android Recovery Menu                                   │
  │                                                         │
  │ > Reboot system now                                     │
  │   Reboot to bootloader                                  │
  │   Apply update from ADB                                 │
  │ * Wipe cache partition  <── [Select to clear OS debris] │
  │   Wipe data/factory reset                               │
  │   Power off                                             │
  └─────────────────────────────────────────────────────────┘

2. Clear Samsung Health App Cache on Connected Phone

1. On your phone, go to Settings $\rightarrow$ Apps $\rightarrow$ Samsung Health.
2. Tap Storage $\rightarrow$ Clear Cache.

When It’s Actually a Hardware Problem

If your Galaxy Watch fails to track sleep, heart rate, or steps even after applying patch CZA6 and performing a recovery cache wipe:

• PPG Optical Diode Failure: Look at the back glass while starting a manual Heart Rate measurement. If the green optical LEDs do not illuminate, the sensor emitter circuit has failed.
• Hardware Diagnostics Menu Failure: Open the Phone app on your watch, enter #0*#, tap Sensor, and select HRM Sensor. If the screen displays a FAIL status or reads continuous zero values while worn, the bio-sensing core is damaged.
• Moisture / Liquid Ingress: If the tracking failure started after swimming or exposure to high water pressure, internal short circuits may have disabled the sensor bus.

If the onboard sensor hardware fails internal diagnostics, contact Samsung Support or an authorized service provider to arrange a warranty repair or sensor assembly replacement.

Sleep tracking dropouts on One UI 8 are primarily driven by a sensor daemon sleep bug that is resolved by updating to firmware version CZA6. Install the maintenance patch, ensure Samsung Health has continuous background sensor permissions, and wipe the cache partition if tracking inconsistencies persist.