samples/net/aws_iot sample strange behavior using nRF9160

Hi, I'm having trouble running the samples/net/aws_iot sample on nRF9160-based board.

Configuration:
- nCS: v2.6.0
- modem version: nrf9160_1.3.6

When running the sample with default settings for a nRF9160-based custom board using provided overlay for nrf9160dk_nrf9160_ns board, I get the following logs:

[Sec Thread] Secure image initializing!
Booting TF-M v2.0.0
*** Booting nRF Connect SDK v3.5.99-ncs1 ***
[00:00:00.253,417] <inf> aws_iot_sample: The AWS IoT sample started, version: v1.0.0
[00:00:00.253,448] <inf> aws_iot_sample: Bringing network interface up and connecting to the network
+CEREG: 2,"CE98","01F62E11",7
+CSCON: 1
+CGEV: ME PDN ACT 0,0
+CNEC_ESM: 50,0
+CEREG: 5,"CE98","01F62E11",7,,,"11100000","11100000"
[00:00:04.385,437] <inf> aws_iot_sample: Network connectivity established
[00:00:09.385,620] <inf> aws_iot_sample: Connecting to AWS IoT
[00:00:13.273,986] <inf> aws_iot_sample: AWS_IOT_EVT_CONNECTED
[00:00:13.274,963] <inf> aws_iot_sample: Publishing message: {"state":{"reported":{"uptime":13274,"app_version":"v1.0.0","modem_version":"nrf9160_1.3.6"}}} to AWS IoT shadow
[00:00:13.352,478] <inf> aws_iot_sample: AWS_IOT_EVT_PUBACK, message ID: 37504
[00:00:13.523,895] <err> mqtt_helper: Socket error: POLLERR
[00:00:13.523,925] <err> mqtt_helper: Connection was unexpectedly closed
[00:00:13.524,475] <inf> aws_iot_sample: AWS_IOT_EVT_DISCONNECTED
[00:00:18.524,658] <inf> aws_iot_sample: Connecting to AWS IoT
[00:00:22.614,288] <inf> aws_iot_sample: AWS_IOT_EVT_CONNECTED
[00:00:22.615,264] <inf> aws_iot_sample: Publishing message: {"state":{"reported":{"uptime":22614,"app_version":"v1.0.0","modem_version":"nrf9160_1.3.6"}}} to AWS IoT shadow
[00:00:22.692,749] <inf> aws_iot_sample: AWS_IOT_EVT_PUBACK, message ID: 16827
[00:00:22.874,816] <err> mqtt_helper: Socket error: POLLERR
[00:00:22.874,847] <err> mqtt_helper: Connection was unexpectedly closed
[00:00:22.875,610] <inf> aws_iot_sample: AWS_IOT_EVT_DISCONNECTED
...

In the AWS I see that the device connects, shadow is updated with the message sent by the device, then the device disconnects with the following log:

{
  "clientId": <hidden_id>,
  "timestamp": 1732104741853,
  "eventType": "disconnected",
  "clientInitiatedDisconnect": false,
  "sessionIdentifier": <hidden_identifier>,
  "principalIdentifier": <hidden_identifier>,
  "disconnectReason": "CONNECTION_LOST",
  "versionNumber": 924
}

Config overlay is as follows (almost no difference between nrf9160dk_nrf9160_ns.conf file):

# General
CONFIG_HW_STACK_PROTECTION=y
CONFIG_HW_ID_LIBRARY_SOURCE_IMEI=y
CONFIG_PICOLIBC=y

# Modem related configurations
CONFIG_MODEM_INFO=y
CONFIG_AT_HOST_LIBRARY=y
CONFIG_NRF_MODEM_LIB_ON_FAULT_APPLICATION_SPECIFIC=y

# Modem trace
CONFIG_SERIAL=y
CONFIG_UART_ASYNC_API=y

# Disable Duplicate Address Detection (DAD)
# due to not being properly implemented for offloaded interfaces.
CONFIG_NET_IPV6_NBR_CACHE=n
CONFIG_NET_IPV6_MLD=n

# Zephyr NET Connection Manager and Connectivity layer.
CONFIG_NET_CONNECTION_MANAGER_MONITOR_STACK_SIZE=1024
CONFIG_NRF_MODEM_LIB_NET_IF=y

# Bootloader and FOTA related configurations

# MCUBOOT
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_MCUBOOT_IMG_MANAGER=y

# Image manager
CONFIG_IMG_MANAGER=y
CONFIG_STREAM_FLASH=y
CONFIG_FLASH_MAP=y
CONFIG_FLASH=y
CONFIG_IMG_ERASE_PROGRESSIVELY=y

# AWS FOTA
CONFIG_AWS_FOTA=y
CONFIG_FOTA_DOWNLOAD=y
CONFIG_DFU_TARGET=y

# Download client (needed by AWS FOTA)
CONFIG_DOWNLOAD_CLIENT=y
CONFIG_DOWNLOAD_CLIENT_STACK_SIZE=4096

# AWS IoT library
CONFIG_AWS_IOT_BROKER_HOST_NAME=<hidden_host_name>

# MQTT helper library
CONFIG_MQTT_HELPER_SEC_TAG=2

Do you know what may cause such error? Are you able to reproduce it? Thanks in advance.

Related