Bug Report: Some paths still dark

Hi, first time submitting anything. I believe paths connected to already completed nodes are supposed to be fixed so you can see the whole path (and the new node at the end), but I'm still running into nodes that I can't see. Not many, mind you, but a few. It's not a game-stopping bug, but I thought it was supposed to be fixed. (is it because I don't have enough sulphite to reach it?)
Just bringing it up.