Ok I have been working on this for months across 4 Linux boxes and this is what I have discovered. It has something to do with sync corrupting .config/opera/Preferences file. Seams if you select to sync the passwords the Preferences file changes the hash for passwords to a sync file and gets stuck or corrupted, I have not figured exactly what is going wrong yet. I have managed to get my passwords back from a backup.
- make sure on fresh boot that opera is not opened at all or this won't work
- Delete or rename the entire opera folder in .config (a hidden folder)
- Assuming you have a recent backup restore this folder from the backup
What I know so far is in the preferences file the password field changes from a 16 digit number and becomes changed to ,"PASSWORD":"SyncEngineImpl" in any password field. From this point forward you can't see your passwords or manage them. The way I am getting around this is keeping a backup of the .config/opera folder and not syncing passwords. Also with the 4 boxes having different versions of 60' something version it effects all of them. I am trying to sort through some old backups and it seems this function last worked with Linux version 52 something. I tried just replacing the Preferences file but this did not work as it is not in sync with the rest of the files in that folder.
One would think the developers would have consider a backup of the directory before a sync process, but no, so do it manually. A easy way is to just copy to a different directory as trying to create a compressed folder seem not to work.
I wonder if they knew they had a problem because sync passwords is not selected by default on first sync. Since Opera has become a chrome one off I am looking into "chrome-pass" just to see what I can help, but the install for this is not well structured. https://chrome.google.com/webstore/detail/chrome-pass-zx2c4/oblajhnjmknenodebpekmkliopipoolo?hl=en