Blyk+dht22+esp8266 any of them... Periodicaly rescive "nan" in value display

Hello dear blynk creators

Got problem with DHT22 and blynk
I use adafruit dht lib and simple timer lib
to do dhtread
but i recive periodicaly “nan” in vaule display widget…

I dont know whatever its a blynk problem or not…

But problem is common, some my friends got such problem to…
i try different esp8266 modification and different dht22 from different shop with same result?

maybe some one already solve that problem?