I'd only recently (a couple days ago) started having this issue as well after installing TMexi's "Clean UI" mod and Zerbu's "All Worlds are Residential" mod. I was able to attribute my particular case to the "Clean UI" mod with Zerbu's mod also installed, as I took both out of my mods folder, deleted the localthumbcache file and then loaded the game. Was able to freely access Copperdale again after that, but did further testing - I closed the game and then put Zerbu's All Worlds mod back in, but not the "Clean UI" mod, deleted the localthumbcache again, restarted the game again. Copperdale was still working as it should.
So, at least in my case - your results may vary - I was able to pin my issues on the "Clean UI" mod.
