If the function collect/accumulate is used in the beta node(left constraint) with expired event, it's sensible to the order of events being inserted, which should not. This issue didn't happen in bpms 6.4. It occurs in rhdm 7.x.
For example:

"import " + DummyEvent.class.getCanonicalName() + "\n" +
"import " + OtherEvent.class.getCanonicalName() + "\n" +
"import " + HashSet.class.getCanonicalName() + "\n" +
"declare DummyEvent " +
"@role( event ) " +
"@timestamp( eventTimestamp )\n" +
"@expires(0ms)" +
"end\n" +
"declare OtherEvent " +
"@role( event ) " +
"@timestamp( eventTimestamp )" +
"@expires(2d)" +
"end\n" +
"rule R0 when\n" +
" $d: OtherEvent() \n" +
" $r: HashSet ( size >= 2 ) from collect (DummyEvent())\n" +
"then\n" +
" System.out.println(\"R0 Fired\");" +
"end";

If you insert events like:
ksession.insert( other);
ksession.insert( dummyEvent0 );
ksession.insert( dummyEvent1);

The rule gets fired. But if you inserts the events like:

ksession.insert( dummyEvent0 );
ksession.insert( other);
ksession.insert( dummyEvent1);

The rule doesn't get fired.