Many thanks you for your answer.
What is very curious is that it have been worked as a charm during 6 month and since a few days, it is always down. I do not change nothing on my wifi.
Each time I look it is down:
And If i interact with the Nuki in bluetooth mode, the reconnection is done and SL3P works as expected for a certain time.
It is likely that SL3P goes to sleep and have to be waken up for reconnection (with bluetooth or whatever).
I will try to wake-up manually.
This can result in longer offline periods if your network turns out to be unstable
Have you more information on this ? How long is reconnection period typically ?