I've just ran the installer, pushed middle button and moved it to the right or to the left, 'MEvent. CASE!' is then written to console.
Cannot reproduce the issue in the latest issue.
In the latest installer, rather.
This is actually an OpenJDK issue: changeset reference here: http://hg.openjdk.java.net/jdk8/awt/jdk/rev/19431d07bc19 Looks like a stray System.out.println() was left in erroneously.