I don't understand. The screenshot TvPlanIt-same-events-1 shows your application at first start: Event2 and Event1 share the same time slot, both are visible, nothing's hidden --> as expected. Then I dragged Event2 over Event3 --> screenshot-2, as expected. Then I dragged Event2 back over Event1 again --> screenshot-3, as expected (well, the order is different -- is this relevant?). And finally I dragged also Event3 over the others --> screenshot-4, again as expected.
Are you sure that you installed the most recent version of TvPlanIt from CCR?