I had my Galaxy S6 protected with a fingerprint lock and also encrypted, requiring a password every time it was turned on. I changed the fingerprint lock to a direction lock and the next time I rebooted it, it didn't prompt me for the password, but rather for a pattern. I have NEVER enabled a pattern lock so this is a bug. It is asking me to enter a pattern that hasn't been defined. Now I have to factory reset my phone. This unfortunate turn of events seems to coincide with changing the fingerprint lock to a direction lock, so I'd be very careful using this unlock mechanism if your phone is encrypted.