Hello, is this thread still alive? (probably not considering how old it is)
Initially this was about Nuki 3.0 Pro and I have found out that since then there have been changes that supposedly adress this issue:
MQTT API is now also working if SL3P has no internet connection (local only)
I have recently gotten my Nuki 4.0 Pro and I am running into this problem again. I am trying to use it locally via MQTT over WiFi and Home Assistant while intentionally blocking internet access for the Nuki on my firewall. (I really don’t like my door lock being connected to someone elses server) A couple minutes after I block the internet connection the connection to home assistant cuts out as well and I see it constantly trying to reconnect.
2024-12-19 01:35:34: New connection from 192.168.188.44:54659 on port 1883.
2024-12-19 01:35:34: Client Nuki_41B58AFC already connected, closing old connection.
2024-12-19 01:35:34: New client connected from 192.168.188.44:54659 as Nuki_41B58AFC (p2, c1, k300, u'user').
2024-12-19 01:36:14: New connection from 192.168.188.44:61382 on port 1883.
2024-12-19 01:36:31: New connection from 192.168.188.44:51468 on port 1883.
2024-12-19 01:36:31: Client Nuki_41B58AFC already connected, closing old connection.
2024-12-19 01:36:31: New client connected from 192.168.188.44:51468 as Nuki_41B58AFC (p2, c1, k300, u'user').
2024-12-19 01:36:45: New connection from 192.168.188.44:55703 on port 1883.
2024-12-19 01:36:45: Client Nuki_41B58AFC already connected, closing old connection.
2024-12-19 01:36:45: New client connected from 192.168.188.44:55703 as Nuki_41B58AFC (p2, c1, k300, u'user').
As soon as I unblock it an re-enable the internet access, the reconnects stop and it shows as available again in home assistant and works great.
Is local only MQTT support for the SL4P just not a thing? Presumably since it has been added for the SL3P I would expect it to work for the SL4P as well, but maybe not?
Would it be possible to achieve local control via thread instead? (would need to get a thread stick or thread border router then for my Home Assistant)
I hope someone can help me here. 
Let me know if we need to open a new bug report / feature request.
Model: Nuki Lock 4 Pro
Firmware: 4.4.9 (latest stable)