It's the boss's final attack. He was attempting to take over your mind. Not a bug, and not really a secret, don't worry, nothing's broken
Sorry I meant screen went to white when the grunts were supposed to come, I'm referencing the boss stage before locking my abilities and forgot to mention, it seemed like he may have been partially invisible(remember thinking hard to see and/or track) and again there's supposed to be a grunt interruption but instead I was still seeing the missile 'x' marks and laser lines, but couldn't see him