If you run into the bug described in the main walkthrough in the room with the Tesla gun and don't have another save you can reload, try this alternate route to the exit. It's tricky, but quite a bit better than having to replay the whole game. If you haven't already obtained the gold reward, you won't be able to get it, but you can at least finish the level and then replay it later.
Thanks to Tom W. for sharing this strategy with me. I believe it was first reported on Tomb Raider HUB.