umqttsimple - network hangs after send ping 4 times

[zygfrydos]

code:
client = umqttsimple.MQTTClient(ubinascii.hexlify(machine.unique_id()), '192.168.2.254',keepalive=100, **{'user':'a','password':'ni'})
client.set_last_will('a/availability','offline',retain=True)
client.connect()
client.publish('a/availability','online',retain=True)
while True:
client.ping();print('ping');time.sleep(1)
ping
ping
ping
ping
Disconnected

when I try ping my esp from other computer I see that esp desapear

I work on esp8266-20200911-v1.13.bin