In the "Time Machine" level, I reach a point in the level where I am supposed to:
Move a boulder in the past, to create a well in the present.
I have watched videos which show how to do this, and yet I can't do it myself. For reference I am currently playing with the Scientist, Twins, and Time Traveler. It seems like when I switch between characters my character in the past may be dying (as in the "poof" that occurs when the environment kills them), but I can't see how. I am also playing on XBox 360 if that helps.