I finally fixed my Galaxy Watch 8's broken sleep data by digging into Samsung's deepest menus

I tried Samsung's sleep coaching after its October update. My Samsung Galaxy Watch 8, however, was flying blind night after night.

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Some mornings I'd wake up to a gap in the middle of my sleep record, and other mornings there was no record at all.

Desperate for a fix, I checked the forums and found other owners with the same issue. Many threads suggest rebooting the watch or wiping the sensor glass, but neither helped me.

I spent weeks fighting with mine, and what finally worked was a combination of settings buried in the watch's menus. But I tried a few quick checks first, though.

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By  Taylor Kerns

Fix the fit before blaming Samsung

Optical sensors need clear skin to work

The Galaxy Watch 8 reads your body with photoplethysmography, which is a mouthful for a basic but brilliant trick.

The BioActive sensor flashes LED light into your skin and measures what comes back to calculate heart rate and blood oxygen saturation.

If the sensor can't get a clean read, the software has nothing to work with. Dark ink is a common blocker.

Tattoos absorb much of the light, which can prevent the watch from detecting your wrist. Dense arm hair and a loose strap can cause the same problem.

If your wrist is tattooed, wear the watch on your other arm or move it to a spot without ink. If arm hair is the problem, trimming a small patch under the sensor makes a noticeable difference.

Restless sleepers have a separate problem. One UI Watch relies on accelerometer data to tell light sleep from being awake.

So a night of tossing and turning is logged as awake time and leaves fake gaps in your record.

The fix is boring but worth doing. Slide the watch higher on your wrist and snug the band up a few notches.

Start here before opening settings, as these fixes take seconds and often do the job.

Power saving can switch off your sensors overnight

Keep the battery savings without losing your data

Power saving on the Galaxy Watch 8 is aggressive. Overnight, it can throttle the processor and background sync, and it can stop the background heart rate tracking.

Go to Settings > Battery > Power saving. Look for the Limit health features option and make sure it's turned off.

It may have switched on after a system update, and you'd never know unless you looked.

This way, Power saving still dims the screen and turns off Wi-Fi, but the watch keeps tracking your heart rate and movement through the night.

The buried permission that finally fixed my sleep data

Background sensor access is what sleep tracking needs

Background updates may revoke continuous sensor access for third-party apps and for Samsung Health.

Without background sensor access, the watch has little more than movement to go on.

On the watch, swipe up to the app drawer and open Settings > Security and privacy. Under Privacy, the Permission manager has a section for Sensors.

Tap Samsung Health and set it to Allow all the time. If you see Allow only while using the app or another narrower option, change it, because background sleep tracking can fail without full access.

It's a little absurd that a sleep tracker can lose sleep-tracking ability through a privacy setting four menus deep, but here we are.

Still broken? Clear the cache, then collect the logs

When nothing works, it might be the hardware

If permissions don't fix the problem, wipe Samsung Health's temporary files. On your phone, go to Settings > Apps > Samsung Health > Storage and tap Clear Cache.

Clearing the cache only removes temporary files, so your sleep history stays put. If that doesn't solve it, back up and factory reset the watch. If the gaps survive a reset, the hardware is the likely culprit.

Before you send the watch in for repair, get an error report. Open Samsung Members on your phone and go to Support > Send feedback > Error reports, making sure Send system log data is checked.

Sleep coaching is only as good as the data underneath

Samsung's October update adds nice features to sleep coaching, but all of it is worthless if the data feeding it is missing hours.

Getting out of basic tracking mode took some work on my end, and it probably will on yours. Start with the fit and Power saving, since they're the easiest to rule out.

If your nights still come back patchy, go to that sensor permission. That setting brought my sleep data back, and it's the difference between a proper health device and overpriced wrist candy.