nRF9160 SIBA unable to connect to NB-IoT network and resets every ~10 seconds.

Question

nRF9160 SIBA on custom board is unable to connect to NB-IOT and resets after about 10 seconds of operation. 
 Without a call to lte_lc_init_and_connect the reset does not happen. 
 The power, as suggested in other topics is at 2.6V from dc power supply with limit set to 1A. 
 Side note: this setting is the only one allowing for the programmer to reach the SiP. At planned 3.3V the programmer is not able to connect to the chip. For now just a missing power IC -> power supply is used.

elephant · Accepted Answer

Just to conclude this. There appears to be some sort of a circuit break inside nRF9160. Most probably due to mounting procedures. 
 This is because antenna and matching network togather, connected to thingy:91 do really work. It connects ok just like with its own antenna. And thingy behaves just like my custom board when the wire is just touching a pad without proper soldering. This thing occurred spontaneously during experiments with the two boards.