Got this testing the 0.95.2 RC.
I killed -STOP a region server and let it stay like that while running PE. The clients didn't find the new region locations and in the jstack were stuck doing RPC. Eventually I killed -CONT and the client printed these:
Exception in thread "TestClient-6" java.lang.RuntimeException: org.apache.hadoop.hbase.client.RetriesExhaustedWithDetailsException: Failed 128 actions: IOException: 90 times, SocketTimeoutException: 38 times,