There is something wrong at Cartagena. Thats a texture error.
I have now confirmed what you are referring to. Turns out it isn't a missing texture, since those show as grey.
Instead, it is missing
geometry, which means there is no surface for a texture to be applied to.
This actually applies to the original game as well, but there you basically never noticed as you get reloaded to another location before you ever get to see it.
But in Cartagena, that corridor doesn't actually lead anywhere, so then you CAN see it.
Three things we can do, in order of time required:
1. Small graphical glitch, so just leave it as-is
2. Make that corridor lead somewhere (possibly even just have it lead back to itself, so you're being turned around 180 degrees)
3. Add a background to the model
I personally don't mind one way or another. But my preference is #1, since I don't want to spend my time on this one.

You could probably do #2 if you like. If you insist on #3, maybe
@Jack Rackham or
@Bartolomeu o Portugues could help out with that?