Short version
This is a feature request to unlock the phone from the lock screen upon a failed fingerprint read attempt if the phone is unlocked anyway due to Smart Lock. The action of holding the finger to the scanner should suffice as a request to unlock the phone in the same way that 'swiping up' on the lock screen does.
Long version
The fingerprint scanner on the Xperia Z5 Compact is built into the power button. When the power button is pressed the screen is turned on to the lock screen, and by holding the finger on the button the phone can be unlocked. This makes a very comfortable and quick way to unlock the phone, as your finger doesn't need to move from the power button. Otherwise, you have to 'swipe up' on the lock screen and enter the pattern or pin.
With Smart Lock, the pattern or pin can be skipped entirely when for instance a certain bluetooth device is near. This can be set up in the Security settings on the phone. The lock screen is still shown, but after swiping up the phone unlocks immediately without the need for the pin or pattern.
Sometimes, the fingerprint sensor fails to read the finger, perhaps because it is dirty or the positioning is less than ideal. When this happens in the lock screen, the phone complains that the finger could not be read. However, it did notice that the finger was present. I claim that it is not relevant whether the finger could be read succesfully by the sensor to unlock the phone in the case that Smart Lock is enabled. After all, a pin or pattern is not required either. Upon detecting the intention of the user to unlock the phone by holding a finger on the scanner, the phone should unlock if the Smart Lock criteria are met. The alternative is that after a couple of false readings, the user should swipe up on the screen to unlock the screen anyway. This is especially frustrating because it adds no security at all, as there is no lock on the phone. Additionally, if the fingerprint scanner fails because the fingers are dirty, this then causes the screen to also become dirty.
Please consider this quick enhancement for a next version of the software! It would be greatly appreciated, as well as increase the perceived accuracy of the fingerprint scanner for people who use Smart Lock.
