Hi there!
my original issue created on github can be viewed here
To repeat:
We are running 2 nodes set as master, with discovery.zen.minimum_master_nodes: 2, one node has low disk space and reaches threshold, occasionally moving shards to the other node.
The issue we have is that the nodes are disconnecting every few hours for period of 15 minutes. This occurs mainly during night when the instance load is minimal.
the log can be seen here