Fingerprint login doesn't work sometimes

I've noticed that if I haven't logged in a while, when I go to login with my fingerprint it says success, but then prompts me to enter the master password.  It doesn't happen all the time, but seems to happen after my inactivity time runs out, although I'm not sure as I haven't specifically timed it.  I'm really hoping that this doesn't mean I have to enter in the master password every single time I login after inactivity runs out.  Can you imagine what a huge pain it is to enter in a long password on the tiny smartphone keyboard?  

Also I notice that if the fingerprint recognition fails once then you have to enter in the master password.  Please consider making this requirement after maybe 3 incorrect fingerprint attempts.  Phone fingerprint sensors can be inaccurate and often the first one fails, once again it's a huge pain to have to enter in the master password.

Thanks.  This is on a Galaxy Note 5.