I recently tried going back through the chapters to get the last few treasures I needed, and I encountered problems with these two chapters. During the start of chapter 12, after beating up the enemies when I climb the crates up, climb the wall and swing on the rope to reach the platform, the door is already open and you cannot advance further, normally Drake would find his weapon holster, but no cutscene plays, I'm just stuck in the room. Its also important to note that there is no sound/music, and Drake's idle animation will freeze in one position.
I also could not play Chapter 18 at all, right at the beginning of the chapter, after he lands with the crate, I'll make my way to the wreckage of the plane, the screen fades out and acts like its going to play a cutscene but instead just remains white, trying to skip the cutscene or quit the game cuases my PS3 to crash and I have to do a hard reset.
Any help would be aprreciated, these are the last two chapters with treasures I need in them.