So this was a permissions issue inside of SMF, and ultimately I'm not sure if the board permissions are even correct, but I have given guests the ability to view attachments on this board. This should fix the issue at least for a couple of boards I've seen in the same state, however not all were like this, only a handful.
We will loop around and double check all of the permissions on the boards to ensure they're properly setup and usable by all.
Cheers,