gunnar You are definitely seeing a bug and I'll need to address it in an update. Thanks so much for discovering and pointing this out to me.
That said, if all you're looking to do is to save a site-specific login name, what you likely should be using as the type for your login name on the site is not "DEVICE" but "OWN".
The difference between "DEVICE" and "OWN" is that the former is a special type of saved information that will never leave your device. Spectre will never include it in export files or backup files. You use the "DEVICE" type if it is very important to you that this information never leaves your device. The "OWN" type is what you typically think of as "saved information". It will be encrypted whenever included in a backup file.
It looks like there is a bug in the application, where the auto-fill Spectre app is not receiving permissions to read the "device"-specific value saved in your login name.
Try setting your type to "OWN" and let me know if that helps?