It's always Abernathy farm and Tenpines bluff, over and over again. Preston tells me the 2 need help. I'll cash in the quests and immediately get the same 2 settlements needing help. What's the deal with this?

Preston's radiant quests been annoying.

Complete them to the "talk to Preston" point then don't bother. Eventually they'll complete themselves and you won't need to go back to get bombarded with another set of the same quests from him.