NUKI 2.0 su firmware 2.11.9 stops working

Hello everyone, i am using NUKI 2.0 with firmware 2.11.9.
I use api http queries every 20 seconds.
Worked great for over two years, now stops working completely every 3-4 days.
The work is fully restored only after removing and re-installing the batteries, and so every 3-4 days.
What is the problem?
Thanks to all.