@tappingtam Long and short of it overall is that it has been reported to be a Chromium issue, though debatable if it’s Chromium, purely Windows DP API (Data Protection API), or something else. But just has been some disconnect between the two where the encryption keys get lost.
99% of the time people see the login data still on their device if you navigate to your profile path, but it’s encrypted and can’t be read due to the encryption key being lost or corrupted.
Using sync has been a way that people have been able to circumvent any issues, as when it gets “lost” and creates a new key, it just obtains the passwords from the sync chain again and things continue to work flawlessly.
If you’re not going to use sync, then you’ll need to be prepared for any potential issue like this to happen or you’ll want to use an external password manager. Of course, regardless of what you do, exporting and keeping the passwords saved somewhere as a backup is usually a good idea.
The sad part is that this has been an issue for several years and absolutely no progress has been made on fixing the issue or preventing it from happening. Well, beyond just having to tell people they absolutely need to use sync, a password manager program/extension, or routinely export passwords for backups just so they have them if something goes wrong.
One day they might figure it out in greater detail. But people generally haven’t been able to replicate it and certainly haven’t identified the driving force behind it when it does occur. Essentially they just narrowed it down to the bit I mentioned.
Other OS haven’t had as much of a problem, though it can still happen if their keyring/keychain has problems. It’s addressed a bit at https://support.brave.app/hc/en-us/articles/29808985123085-Sensitive-data-storage