(GSS)[6.4.z]DrlParser/DrlDumper will break valid DRL containing accumulate statements

When parsing and then dumping a valid DRL containing "accumulate" statements, will throw exception while building kieBase.
~~~
java.lang.RuntimeException: Build Errors:
Error Messages:
Message [id=1, kieBase=defaultKieBase, level=ERROR, path=rules.drl, line=24, column=0
text=[ERR 102] Line 24:13 mismatched input ':' in rule "last flown date"]
Message [id=2, kieBase=defaultKieBase, level=ERROR, path=rules.drl, line=0, column=0
text=Parser returned a null Package]
~~~

This issue is not reproducible in BxMS 6.3.x release. It occurs only in 6.4+ releases.