BC66-TE-B-KIT Budget Link


I’m using this module to collect data on signal quality and bit error rate in different conditions.
I intend to use this information on my dissertation.
Unfortunately the module is not able to register to the network when the conditions are not favorable (for example if I am not able to get 4G on my phone due to distance or loss of signal in an underground environment, the module also loses signal and cannot register to the network). According to the information I gathered about NB-IoT, the budget link should be enough for the module to be quite resistant to this conditions.
Am I doing something wrong? Can the problem be the network and BS it is connecting to?
I am using Arduino and this project by Wiz-IO to connect to the network:

I am also using the following command periodicaly to obtain the information: AT+CESQ

Any information on this would be helpful.
Thank you.

the cell radius aprox is 2 km @ 900 MHz… with good antenna
( my tests in city )

and test PlatformIO port ( from my git ) … support firmware v10
Arduino port is very old project - support only v4 firmware