The timeline is not corrupt, it is a simple user error. Could be a transparency issue but more likely you are just not moving the keyframes along with the layer. Without looking over your shoulder or knowing anything more about what you're doing than what you've provided, no way for us to know.
What bogiesan said. You screwed something up, but without seeing the setup there's no way for anyone to advise. could be some keyframe, could be a broken expression (if it's based on an animation preset), could be a million other things. A screenshot might help...
My teacher figured out the problem. Since the type layers were 3D, for whatever reason when I was duplicating the layers the type started behind my background layer then came through it. I tried to give you gifs yesterday, but this site doesn't support them. Anyways, thanks...