Publishing data using MQTT on nRF9160 fails with random message ID

Question

Hello, 
 I am working on an application that runs on nRF9160 using nRF Connect SDK V2.4.0. This application uses NB-IoT connection and has a stable connection to an MQTT broker. I want to publish data to a topic periodically using a timer every 2 seconds, but I am facing a problem with the publish function. 
 Code 
 I have followed the exercise of the cellular course on Nordic Academy , and I am using the same publish function as in the solution. Here is the code snippet: 
 int data_publish(struct mqtt_client *c, enum mqtt_qos qos,uint8_t *data, size_t len, uint8_t *topic)
{
	struct mqtt_publish_param param;

param.message.topic.qos = qos;
	param.message.topic.topic.utf8 = topic;
	param.message.topic.topic.size = strlen(topic);
	param.message.payload.data = data;
	param.message.payload.len = strlen(data);
	param.message_id = sys_rand32_get();
	param.dup_flag = 0;
	param.retain_flag = 0;

data_print("Publishing: ", data, len);
	LOG_INF("to topic: %s len: %u",
 topic,
 (unsigned int)strlen(topic));

return mqtt_publish(c, &param);
} 
 
 Problem 
 The problem occurs when I call sys_rand32_get() to generate a random message ID, the board get rebooted without viewing any error message in the logs. However, when I use a static number instead (e.g. param.message_id = 7; ), the publish succeeds but only for the first time. I have enabled these two config parameters: 
 CONFIG_ENTROPY_GENERATOR=y
CONFIG_TEST_RANDOM_GENERATOR=y 
 
 Additional information 
 I have also subscribed to another topic and the message receiving works fine. Moreover, the publishing using a button works with the same publish function, as shown in the exercise. 
 I have tried this on NCS V2.5.0 and V2.4.0, and I have also tried changing the implementation following the Zephyr RTOS publisher sample , but the problem persists. 
 
 Could anyone please help me with this issue? I appreciate any suggestions or solutions. Thank you very much.