This link posted above stutters reliably on my box, always at the same spots: https://go.ludotune.com/hui4

Win10, FF 91.0.1 64-bit

Stutters at ~24 seconds, ~32, maybe 1:30ish, 5 seconds after that... then I lost track. Not very often but when it does it's very jarring. Happens if it's running in the foreground or background, even if I'm not moving around or anything, just listening with tab in focus.