I forget the name of this area (Nameless Something?) but the one NE of town, near the end of it at the prison. It is very rare for the map to actually display the name of an area which would be a helpful fix; kinda just have to float around trying to get it to pop up, and it usually only shows Area:Safe/Moderate/Etc without the name.
Anyhow, this chest is inaccesible when it spawns, it has happened to me twice now:
