I have this issue as well.
I play PS4 Pro.
When I first time arrived at the signal tower I was able to pick up all collectible items except this one very chest.
After I learned that it is a bug, I did the following:
- reload my last save
- reboot my console
They didn't work. But the corpse nearby the chest is lootable after every reloads. I have now several Pang of Conscience - silver swords and letters of apology other. Also every time I reload the other chest next to this corpse is almost re-lootable. The button appears but then goes away.
I think that the bug has something to do with this corpse and maybe the other chest as well.
I hope this helps you guys to solve the bug.
Actually, and this is still deduction, not official, I think it's the way the game is updated. Perhaps completely uninstalling and reinstalling the complete package upfront may have an effect, but if I'm right, it would require beginning a brand, new game.
If your game was started in one version, then updated, then the files that introduce the Wolf School gear were added via the DLC, then the game was updated some more, and/or more DLC was added as it was released...I think that's most likely why it happens. Even if people install absolutely everything fresh, there may be reference data in the existing savegame files that will continue to manifest the bug (similar to modding issues).
End result is, no one was able to uncover the source of the bug. It simply shouldn't be happening, but it is.