Remotely closed RemotelyClosedException

Could you help analyze this stacktrace what could be the root cause of this exception?
if http requests reached to target servers? 
For context: this doesn't happen all the times. 
```
Caused by: org.asynchttpclient.exception.RemotelyClosedException: Remotely closed
	at org.asynchttpclient.exception.RemotelyClosedException.INSTANCE(Unknown Source)
```