Back to my question. I have ESP8266 with mos onboard. It's connected to AWS IoT. So far so good but periodically (ca once per 3-5 minutes) I got the following output:
mgos_mqtt_ev MQTT Disconnect
mqtt_global_reconnec MQTT connecting after 2157 ms
mqtt_global_connect MQTT connecting to xxxxxxxxxxxxxx.iot.xxx.amazonaws.com:8883
SW ECDSA verify curve 3 hash_len 32 sig_len 71
SW ECDSA verify curve 3 hash_len 32 sig_len 70
ATCA is not available (-20096), using sw ECDH
mgos_mqtt_ev MQTT Connect (1)
mgos_mqtt_ev MQTT CONNACK 0
mgos_mqtt_ev Subscribing to 'mytopic'
mgos_mqtt_ev Subscribing to 'esp8266_xxxxxx/rpc'
mgos_mqtt_ev Subscribing to 'esp8266_xxxxxx/rpc/#'
Unfortunatelly, during this "dead time" ESP8266 does not accept messages for the topic "mytopic". Any guess on it? Thanks in advance!