Found 2 issues with hclust-lw, that might be related. In many cases, the hclust-lw function returns a nil where it should return a node. As a result, some nodes are not represented in the final tree visualization. For some example code with output, see this gist: https://gist.github.com/jandot/99509f603d3335a84671. In addition, this function sometimes returns a NullPointerException. See the same gist for a full stack trace.