Hi Matty,
There wasn't a level 10 boundary for Redcar because there is no Redcar town/parish council. What source did you use to establish that this is the boundary of "Redcar"?
Also, it is "traditional" to re-use boundary segments where that makes semantic sense. In this case, if "Redcar Town Council" should come into existence, its boundary would be shared with the adjacent admin areas, so there is no overlap possible.