There are two configurations where I have experienced this:
1) The Zookeeper leader is removed from the ensemble and a new leader is elected.
Result: Master immediately goes down along with the tablet servers.
2) According to http://zookeeper.apache.org/doc/r3.4.5/zookeeperAdmin.html, the leader should not serve clients in 5+ node ensemble (zoo.cfg - leaderServes=no). Accumulo does not seem to anticipate this situation, so perhaps when a node is removed, the clients attempt to reestablish connection at the leader, who is not serving, and they fail. This may appear as two failures in the ensemble.
Result: Tablet servers die who were clients of the removed node. If the master was one of the clients, then the cluster goes down.
Zookeeper 3.4.5 - 5 nodes with 4 processors and 6GB system memory (-Xmx4096m -XX:ParallelGCThreads=8 -XX:+UseConcMarkSweepGC)
CDH 4.3 - MRv1, no YARN - no special configuration
Accumulo 1.5.0 - adjusted for system memory