Backyard Privacy Fence There Is A Broken Wooden Post On The Privacy Fence In The Backyard. Who's Responsible For Repairs?

There is a broken wooden post on the privacy fence in the backyard. Who's responsible for repairs? - backyard privacy fence

I always thought that if the contributions are on my side of the fence, the wall belongs to the neighbors as they are the most beautiful, with a face made of soft wood.

Any tips on how to obtain this fix? Involve your neighbors? This could set cost for someone?