cluster becomes unstable right after create any bucket in ec2

Install couchbase server 3.0.0-360 on 4 nodes centos 6.5 in ec2.
Run sanity test.
At xdcr test
./testrunner -i fournode.ini -t xdcr.biXDCR.bidirectional.load_with_async_ops,replicas=1,items=10000,ctopology=chain,rdirection=bidirection,doc-ops=create-update-delete,doc-ops-dest=create-update-delete

the test failed.
Stop the test and try on cluster.
Delete bucket. Then recreate the bucket. Right after bucket created, cluster becomes unstable
Live cluster is available at

1 = ec2-54-80-89-59.compute-1.amazonaws.com

1. short public IP 54.80.89.59
2. private IP 10.124.147.134
   2 = ec2-54-196-7-19.compute-1.amazonaws.com
3. short public IP 54.196.7.19
4. private IP 10.88.233.18

use QA key to login to vms