Disk filled up on only one node in cluster

We have a cluster running couchbase 2.2.0 enterprise edition.
We had 2 nodes on that cluster and added a third node a few days ago.
Since then one of the buckets of the cluster on one of the nodes increased its disk usage significantly and filled the disk of the node.
The other nodes are functioning properly and disk size is stable.
What can cause such behavior and how should we recover from it?