Watch series 3 update to 8.7.1 bricked my watch

My watch stuck in the state of trying to update to 8.7.1.

I have watch series 3 WiFi 8GB 38mm on watchOS 6.3. It was paired with iPhone 7 on iOS 14.4.

After I updated iPhone to the latest iOS version 15.7 it refused to work with the watch and requested me to update the watch to latest watchOS. Also the watch began to restart itself every few minutes when simply being on a charger which didn't happen before.

So I started the update process and during downloading the watch kept rebooting itself (cause it's on a charger and paired to iOS 15+), after somehow passing the downloading phase it came to prepare phase and still continued to reboot itself indefinitely (all I see on the display is the same picture or apple logo during reboot).During all night it didn't managed to finish preparation and because I needed to use a phone I cancelled the update and unpaired the watch.

I tried again and again, I tried all the recommendations - official Apple ones, from the internet, from youtube etc. Nothing helped me so far. I'm trying multiple times every day since 3rd of October.

Here is what I can tell about what I've tried and what I've noticed (further the term "paired" for the context of iOS 15+ means not fully completed state of paired watch but only state right after the beginning of pairing when iPhone did connection with the watch):

• watch can pair with iOS 14.4 without any problems because I can skip the update and just pair it
• I can't update watch with iOS 14.4, it asks me to update iOS first.
• tried iPhone 7 iOS 15.7, iPhone 11 Pro iOS 16.0.3, 16.1 (I paired watch when iPhone was on 14.4 and tried update - no success, updated iPhone to 16.0.3 - no success, updated to 16.1 - no success), iPhone 13 Pro iOS 15.6, 15.7.1, 16.1 - no success
• tried multiple full resets of the watch even 2-3 times in a row between update trials
• tried removing the watch from iCloud, removing backups from Watch app
• tried removing and reinstalling the Watch app from iPhone
• tried on and off the charger
• tried hard reset of iPhone and watch
• tried different Apple IDs, different timezones, locales. Physically I'm in Tallinn (Estonia)
• tried different WiFi locations (carriers), 2.4 GHz and 5 GHz
• tried update from the watch itself when it's paired to iOS 14.4 - no success - it says that it can't find the update. Also tried when it was still paired to iPhone that was recently updated to the latest iOS version 16.0.3 and the update process passed download stage but after self rebooting it started download again, and it continued to do so indefinitely, free space was about 2.0-2.1 GB
• tried to switch off auto-locking of the screen on iPhone and leaving with fully charged watch both not on the charger for the whole night - in the morning both were not discharged and update still was "preparing"
• tried resetting iPhone to factory settings multiple times
• the update file size is 1.3 GB. Free space after download is about 2.0-2.1 GB. Once it was 1.9 GB and I got a message that it requires at least 2 GB. This info I got from the few attempts to update directly from the watch, I checked the free space on a device.
• noticed that the problem with self rebooting occurs only when watch is paired to iOS 15+ and is on a charger. There is no such problem if it's not on a charger, or not paired, or paired to iOS 14.4.
• noticed that it seams there is no problem in downloading the update, it just fails to process update file and falls into the reboot
• noticed 1 time after all night of updating it showed me the message that it paused the update and it will continue after I connect iPhone back to the network. Obviously, I checked - there was no problem with the network.
• noticed that if I leave devices, they are not actually doing the update for all the time. It seams they fall asleep. I caught it multiple times to showing that same picture on the watch but the moment I unlocked iPhone to check more details - iPhone starts to check the status and the watch does reboot immediately. That makes me think that they where not doing the update until I interact with them.

This problem should be fixed rather with iOS update or watchOS update which will be focused to solve this issue.

Currently I have my device in absolutely good physical condition but I can't use it at all because of the software issue. I'm sure its not some big bug. Apple should solve this issue. I have a problem which is not my fault but software update which forced me to start the process which killed my device. And now I've wasted a ton of personal time trying to solve the problem. I feel myself humiliatingly by Apple product.