I found something I guess?
If you take the path to the nailhammer effect puzzle and have the effect equipped. The corpse in the vault might start to twitch. When it twitches you can step on it. It might look easy in the gif, but it actually took me some time to get in there.
Repeated gif of the twitch. It only happens once, but the gif is repeating so it looks like she is having a seizure. Which is sending chills down mine spine..











