4 red lights taking diamond formation flashing alternately vertical to horizontal

The witnesses Mr & Mrs B, returning to the Isle of Lewis aboard the MV Loch Seaforth, North Atlantic. They could not define a shape or height but felt that too be seen from their distance the lights would have to be at least 500 feet altitude , due to distance from the ship (estimated 1 mile) as it was still dark and no horizon visible. Also they are certain it was not another vessels running lights but unsure if it was 1 object only or 4. When first sighted the lights were travelling at some speed horizontal then slowed and adopted a strange forward bobbing motion. The lights were lost to view as the ship began its approach to the Ferry Terminal