Drag-n-drop task to calendar creates duplicated events

I'm new to Offlight, so I'm not sure how it should work correctly.

Dragging a task to the calendar view creates two entries - one is an Offlight Task, the other is a calendar Event, as far as I understant. They're the same, with a difference that if I move Task, it only moves that Task, but if I move Event, it moves the Task. Also, it is possible to do this Task multiple times.