Loading in video games: an example

Last month I talked about loading screens and how the 'Jak' games don't have any and 'stream' the leveals. My copy of Jak 3 is a bit scratched(it's secound hand) and although I had no issues during the games main story, I did have this weird glitch yesterday:

This happened when the game failed to load the next area so I could sneak around where they would normally be a wall.