I think I've encountered a glitch. After the mission when you defeat Phantom for the "first" time, you hit the eyeball and it opens, revealing a whole bunch of enemies.

Well, Dante was in DT, and did an impaling move on an enemy when suddenly, he went through the ground, and I couldn't see him. I could still move the camera around; it was as if he was underground.

After the time limit expired, I saw nothing but blackness on the screen, except for a tiny white dot. I started pressing the fire button, and the camera focused on the dot and grew larger, until it revealed Dante falling in darkness.
When I stopped shooting, Dante grew smaller and smaller, until he was a speck on the screen again.

Anyone else encounter this, or any other kind of glitch?

I can honestly say I have never come across a glitch like that before. Maybe it was just a one off thing.

Come to think of it I've never seen any glitches in this game.