Periodic Node Failure - Where to start debugging?

4.0.0-4051 Community Edition (build-4051)

One of our nodes periodically fails, bringing our site down with it. I don’t know much about CB but have inspected the logs in /var/log/couchbase on the failing node and am not sure what to look for to determine the reason for the failure. I have also run cbcollectinfo and have that if someone knows where to start?