According to a post on Reddit by u/ashfleeburgooben, ”Updated my watch last night to 8.3, set it on my 3rd party charger this morning, came back after an hour and it had gained maybe 2%? Tried the same thing with my spouse’s watch and her 3rd party charger with the same result. Put them on the official charger, zoom, done charging in no time. Argh!”
The post goes on to add that upon further testing, it appears that while initially it appeared that the watch was charging albeit extremely slowly, it was discovered that the watch would actually stop charging after a few minutes. This seems to have affected users who bought 3-in-1 chargers, although they note that their iPhones still charge fine using those chargers, it’s only the Apple Watch that was truly affected.
It is unclear what happened in the update that caused the Apple Watch to no longer accept third-party chargers, and if this was intentional or if it is a bug. Either way, if you’re an Apple Watch user using third-party chargers, this is an issue you’ll want to keep an eye out for.