The most intriguing aspect of this bug is that it is seemingly absolutely random. It has only affected a certain number of users, with no obvious explanation as to why and what triggers it, not even a firmware update to blame it on. What’s more, it appears to be affecting both iOS and Android phones alike.
Once the Fitbit Charge 5 is disconnected from a user’s phone, all live and historic data stops syncing. The classic “turn it off and on again” approach is also failing to work its miracle magic in this case, at least for most. Your best bet at the moment is to contact Fitbit support, where they could give you more information regarding the issue.
Fitbit has not made any official statements about how long this fix would take, but if you are an owner of a Charge 5 and affected by this bug, at the very least you get the peace of mind that it is being worked on. The aforementioned post from the Fitbit forum moderator says the company is “working to bring a fix to all our affected members.”