WSREP: failed to report last committed and stop
warning WSREP: Failed to report last committed


This is just a warning, and in itself isn't a cause for concern. I think it's unlikely that this caused the node to stop. See also Percona's blog post about it. 

And then:


  mysqld_safe Number of processes running now: 0


Again, according to Percona (Support):


  Your mysqld process was killed, most likely by OOMkiller. Check the system log. Joining node will refuse to accept connections until it synchronizes with cluster.