Working memory is not disposed when releasing the RuleSession

Under heavy load conditions I encountered high cpu and hangs of the system. A thread dump shows all threads being stuck in
java.util.WeakHashMap, which is called from AbstractRuleBase.addWorkingMemory (please refer to linked thread).
After digging into the code it turned out that the client session object (AbstractRuleSessionImpl) has a release method. This method is supposed to releases all resources used by this rule session. And so it sets the properties, the working memory and the RuleExecutionSet to null:

public void release()

{ this.setProperties( null ); this.setWorkingMemory( null ); this.setRuleExecutionSet( null ); }

However, it does NOT dispose the working memory as expected.
I added the following line to method:
getWorkingMemory().dispose();

Afterwards things improved significantly.