Tumba de la princesa

[Jakobb]

The game is telling me I haven't completed Tumba de la princesa. Yet I go to the site, the cave network, and I can't find it -- I always end-up in a watery cave that's a dead-end. And every time I look online and it shows me pics of it, I know I've already done that one.

Is there some known glitch where you do that tomb but it doesn't trigger as done, or is there another tomb in Altoyaku that is very close by? (Or are online guides rubbish and showing the wrong fotos for what I am looking for?)

[similarly]

As I recall, there are TWO tombs that are right next to each other.