I have a strange problem at the moment.
Im running an MQTT server on a raspberry pi connected to my home network.
This work really well and i can test with any MQTT publisher and messages are received very quickly and consistanlty.
I am using a NB-IOT Device to send MQTT packages to the raspberry pi broker, as shown in this user manual https://www.dragino.com/downloads/downloads/NB-IoT/NBSN95/NBSN95_NBSN95A_NB-IoT_Sensor_Node_UserManual_v2.1.pdf
Everything works but the time it takes to connect to the broker is very inconsistant.
Here is a screenshot of the data usage on one of my NB-IOT Sim cards.
The transmission only takes about 5 secconds and so a normal session time should be around 10-15 secconds to connect to the broker and transmitt the data then receive the acknowledgement.
Sometimes it take 30-40 minutes to connect to the broker.
Ive checked signal strength on the device and it seems to be fine.
Does anyone know if i can check anything else?