(29 Oct 2020, 8:10 pm)RobinHood wrote 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.

Sometimes, but not always. 
In the case I provided, the section west of Chester impacts on the rest of the route. 
The variation to the route and consolidation of daytime routes in to the 78/A ensures its timings are as they are on an evening.
I'd need to check the eastern portion (or someone else can), to see whether there's any pattern or syncing with the 4 between Woodstone Village and Shiney, with the 2 between Shiney and Sunderland or any of the local routes along Chester Road within Sunderland.