The error "ERROR: Failed due to unreachable impalad(s): x.x.x.x:2200" occurs when one of the impala daemons are not reachable. So queries which try to run fragments on this impalad will fail and hence the query since it is not reachable.
If you are facing the unreachable error for only one host - To keep things rolling, you can try stopping the impalad on this specific host and try running the query. This way the queries won't try to run fragments on this impalad and should run fine.
To find out the cause, you might have to check the connectivity to this affected impalad on port 22000.