The "April security patch" is the responsible for the lockscreen/fingerprint problems. Those of use who use Nova Launcher and have double tap to sleep will now get a message saying that we can't unlock the device using the fingerprint because of a new security protocol. The fingerprint will only work if you turn off the phone with the power button. If you use Nova's double tap to lock (or any other 3rd party app) the fingerprint won't work.
And it absolutely s*cks. I'm trying to find a way to revert back to the March update. In the meantime I've basically disabled the fingerprint scanner on the lockscreen. It's bad enough Samsung removed the double tap to wake. I'm not willing to lose double tap to sleep too. I rather keep the apps with sensitive information under the fingerprint lock of App Lock than to lose double tap to sleep too.
This is the sort of pathetic thing that Samsung SHOULD avoid doing. They clearly aren't smart enough though.