This particular service has always been liable to have / cause problems, for as long ad I can remember. The one before is usually OK but as you say it tends to bugga up subsequent services and you have to wait until a much later one until punctuality resumes.

I presume this is something to do with where it comes from, whether the inbound train that becomes this service is itself delayed or because there is a conflicted movement that delays it. Basically comes down to insufficient slack in the system.

Despite this, they keep running it unchanged. Isn't keeping doing the same thing and expecting a different result one definition of madness?!