been trying to apt-get --reinstall some things to see exactly that

rootsh reinstalled fine.
File box runs into the problem and says can't remove /etc/sudoers.d/filebox.sudoers.
I made a backup then deleted the contents of sudoers.d tried it- same error.
put a blank file in there with correct name - same error
copied the right file back- same error

Tried it with cleven error same (except same it can't find /etc/sudpers.d/cleven.sudoers)

reinstalling conky worked fine.

reinstalling yosmapa worked fine.
My conclusion is that etc/sudoers is just not visible
If an app doesn't need to use that folder then it installs and updates fine. If it needs it then it returns an error. How to fix that is the big problem lol.

I've tried running update-sudoers and it seems to work but nothing changes. ( don't really know what that's supposed to do though.)

EDIT: further experimenting suggests, from putting other files in there, that whatever I am trying to install/update just returns an error based on the name of the files. So if there is a.sudoers, b.sudoers and c.sudoers and I try to update program x - it will same error can't find a.sudoers no such file.
If I delete a.sudoers then it throws up can't find b.sudoers instead.