Restoring data is a simple file replace operation. Your current database is completely replaced by whichever data file you choose. No checks are made that the database is a valid Password Safe file. Any file with an extension .db can be restored but of course only a valid Password Safe file can be opened by the app.
If your app crashes or contains unexpected data then you most likely have not restored the file you intended.
For example, depending on certain app settings, a backup to Dropbox can place the backup file in different places on different devices.
Check for other backup files. You may not be using the one you think you are. To confirm this, create a uniquely named folder and place your backup into this folder. This way, when you locate the backup within the app, it will always be inside the folder you created.
If you are changing phones, backup to this unique folder on your old device then restore from it on your new one. This will ensure that both devices use the same file.
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