java.lang.ClassCastException: org.drools.reteoo.AlphaNode$AlphaMemory cannot be cast to org.drools.reteoo.BetaMemory

When trying to add a rule package to a knowledge base I previously removed a used knowledge session from, the following error occurrs:

java.lang.ClassCastException: org.drools.reteoo.AlphaNode$AlphaMemory cannot be cast to org.drools.reteoo.BetaMemory
at org.drools.reteoo.NotNode.updateSink(NotNode.java:461)
at org.drools.reteoo.RuleTerminalNode.attach(RuleTerminalNode.java:347)
at org.drools.reteoo.builder.ReteooRuleBuilder.addSubRule(ReteooRuleBuilder.java:174)
at org.drools.reteoo.builder.ReteooRuleBuilder.addRule(ReteooRuleBuilder.java:134)
at org.drools.reteoo.ReteooBuilder.addRule(ReteooBuilder.java:113)
at org.drools.reteoo.ReteooRuleBase.addRule(ReteooRuleBase.java:445)
at org.drools.common.AbstractRuleBase.addRule(AbstractRuleBase.java:952)
at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:629)
at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:472)
at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150)
...

This issue doesn't seem to happen on 5.4.0.Final but it does appear on 5.5.0.Beta1 and on branch 5.4.x

I attached a project (P8.tar.gz) that allows you to test this issue. Any help would be appreciated