fluid marlin
I'd estimate about 1/3 of the successful runs I have end with the Emperor Shade going into the Lumin Vase in slow motion. I haven't been fast enough to capture a video but I don't think you really need to see it to understand. It's like when the boss dies and you get a moment of slow motion, except it's happening when it's not supposed to after pressing the button (I'm using a controller) to lift the Lumin Vase.
This is not really a problem of any significance, and I don't really care if I have to wait a few more seconds at the end of the game, but it's technically a bug so I figured I should report it. There doesn't seem to be any trick to reproducing it—just that it happens fairly often. I thought it might have something to do with when I press the button to lift the Lumin Vase but that doesn't seem to have anything to do with it.