Sometimes situations like this come about as buses are aligned into frequencies elsewhere along the route.

Back when Arriva operated the 81 to Stokesley, it ran 5 minutes ahead of the 28A, with nothing for 55 minutes towards Great Ayton.

When I queried it, they told me that the times of the 28A we're fixed by the times it operates back into Middlesbrough to fit a headway there with Service 28/29. The 81 was timed to run opposite the 28 around West Guisborough, and because of this, the fallout was the 81 and 28A ran together when they met at Great Ayton.

It's not ideal, but it made sense when it was explained.