Dragon32 emulated via Xroar using .vdk:
At around 28k, I experienced some funky business going on with, apparent, invisible asteroids. I'd clear the screen but wouldn't advance to next level. Firing blind, I'm able to hit something, I see explosions, but no asteroids. A few mystery hits and then I can advance.
https://www.twitch.tv/videos/1873140906?t=00h35m26s