Managed to find something at the location shown in this screenshot which will allow you to get that last 2% of the map. (make sure to exit outside the Tomb and then back into the Tomb through the main entrance for 1% of the map also). For some reason this was not counted as a secret, but it should have been, since i was not even looking for this given i had 6/6 secrets already. basically stumbled onto it by pure chance.