Hello Tobias,
Please read thought the guidelines on how to become a Nuki tester and receive the latest Beta in the link Below:
How to become a Nuki Accessory (Fob, Keypad, Door Sensor) tester
Looking at the issue you mentioned, this Beta does not provide any specific improvements regarding Fingerprint sensor.
Please stay tuned for the upcoming improvements in this regard.
Thanks for your support,
Daniel