One of the most common mistakes or forgotten settings is most likely the master/node ratio.
Avoid Vote Ties
Elasticsearch nodes vote for a master node. One needs to make sure that minimum_master_nodes is greater than the total amount of nodes / 2.
If you don't have enough datanodes to counter this, consider adding a dataless node. This way, master election will occur when only one host is down and you can still accept writes.
node.name: "dataless-node-0"
node.data: false
Also as a small reminder from my previous blog-entry: Don't forget to set the heap-size to around half the amount of available system memory (and less then 30GB) and possible disable swapping.
export ES_HEAP_SIZE=10G