I'm having this exact issue. I can still see Aku Aku which makes it even weirder - there just isn't any light after the rats.When I think of Crash 1 I always think of struggling with those bouncy barrels on Toxic Waste as a kid, didn't even get me once this time, easy colored gem.
On Lights Out, no matter what I do the light from Aku Aku always disappears at the last section just as I jump into the area with the rats before the pendulum blades, don't remember that, am I being too slow or something?
I think it's a glitch, since it looks weird with the steam etc still being lit, and this video doesn't have the same problem.
Edit: Just completed the level. It's a time limit as you said. I managed to complete the section before faster after picking up Aku Aku and the final few jumps were still lit. It really should be clearer about that though, especially since Aku Aku still follows you and makes it look like the way forward should be lit.