When adding a client admin to a Location I would expect that client to be able to view all tickets that are assigned to that location. The feature only works for me when I also make the client an admin for the Department as well. Can't you just do Client Admin for locations only?
I have the same issue and I suspect that this is how it was originally intended as previous help desk versions seem to have the same issue.
I'd recommend raising a ticket with support for confirmation and a workaround (if any) available for this. Additionally a feature request would be a good way if multiple users are having the same issue and would like the same feature.