Couchbase cluster rebalance stuck

I am having a couchbase community edition cluster which is giving too many issues since a couple of days. There are frequent error message box shown below:

And randomly one of the node will get fail over without the server actually getting rebooted. Later when I had to rebalance the cluster, its stuck with rebalance since more than 1hr now and there are no other options enabled in the web panel. The below is the screenshot of the cluster with rebalance stuck.

The logs are too full with errors that keep repeating.

All the servers are hosted on Ubuntu 14.04 at MS Azure. How to fix these issues?

Edit: couchbase community edition v4 is being used.