Guiltythree
What if what he saw in his soul cores was something weaved into in soul by someone ? Like the "Fated" ability. And that's what the bird took. Maybe the glitch the spell underwent is an unability to assess Sunny ability in changing fate in this nightmare (as nightmares do) because he litteraly braked away from it. If Sunny is the only human being that is not affected by fate it would make sense that the Nightmare spell can't assess him anymore. Just speculations btw