I've checked reg $22 and it does turn off ULA VBlanking. If I force it off, the game doesn't work at all.
The game also doesn't write anything other than 0 to this register, so isn't disabling it anyway.
How does the copper do the audio exactly? I am hearing sound effects on mine..?!?! (door open etc)
Unless I'm running an older version... But it looks like the one I'm running.