enq: HV - contention

I am testing on X4-2 ExaD and seeing major contention on the cluster using 12.1 of the database.  We are running a DOP=192, bigfile TS with 32K blocksize.  Using TEMP groups for user temp area.  Here is the statement that is 100% contention in the cluster.

insert /*+ append */ /* rule: THINGSAM */ into MDSYS.RDF#13 (start_node_id, p_value_id, canon_end_node_id /* NGLI_PJ */ ) select s_id, sys_op_numtoraw(6459981115371763560), s_id /* NGLI_OS */ from ( select /*RULE_HINT*/ distinct start_node_id s_id /* NGLI_IS */ from ( select start_node_id, p_value_id, canon_end_node_id, null AS distance from MDSYS.RDF#13#2 s union all select start_node_id, p_value_id, canon_end_node_id, distance from MDSYS.RDF#13) m1 where p_value_id = sys_op_numtoraw(834132227519661324) and canon_end_node_id = sys_op_numtoraw(4016149533173549788) /* NGLI_AP */ ) where not exists ( select /*+ HASH_AJ */ 1 from ( select start_node_id, p_value_id, canon_end_node_id, null AS distance from MDSYS.RDF#13#2 s union all select start_node_id, p_value_id, canon_end_node_id, distance from MDSYS.RDF#13) x where