I'm on that mission right now. If you think about it, it's a really good time to end the game. It's a like a big crescendo; just as when your getting used to the texture blur pop-ins...BAM! Low res textures mofo! The two really compliment each other.
lol. i know, right? ...i can't believe how much this cost me.
I had the same issue, but right before you get the defib. I loaded an old save from when I just got to Wellspring, then did all the missions _before_ Defib Upgrade, and then it worked okay. Overall, really disappointing.