We ran into other issues with 4.0.0.0 -- related to how the cluster members talk to one onother -- they seemed to argue about which was the master and occasionally one would "win" by starting a new cluster and the others would move to it.
Now that you mention it, we knew it was happening because we lost the ability to authenticate to the new clusters.
We moved to 4.0.0.4 and the problem hasn't resurfaced.