Here is a better method. The idea is to do bootstrapping aggregation for the fingerprint using your three profiles.
Delete all your fingerprint profiles.
Create your first profile: this must be representative your finger, so place your finger in the different positions that you normally use to unlock, and with different pressures on your screen. Now that you have set your profile 1 use it as normal.
Once the sensor starts to consistently fail ( not just one failure but a considerable amount of consecutive failures) set your profile 2 mirroring the same conditions that led to the fingerprint sensor failures.
Repeat for profile 3.
If no consistent failure is found after your second profile is done you can do an outlier profile.
Each sensor failure will normally occur when using the edges of your fingerprint. So when scanning your finger for profile 3 use only the edges of your finger to create the profile.
Following this I managed almost 100% correct detection
I have had my a70 for roughly 4 months and have had various software updates throughout that time. Each update seems to affect the fingerprint sensor. They have all improved each time, up until the last one which has made it unusable. I am now using face unlock. When I first got the phone it would constantly unlock in my pocket and call people etc. I have had many samsungs and never owned an iPhone, however this phone, apart from the battery has been abit disappointing and I'm now considering a switch. I just want a phone that works and doesn't over complicate things.