I spotted the bug as well on a custom-made Chromium-based browser. This took a while to track down. I was combing through everything that could be related to variables or calling on the function names, but I could not locate any problems. When I noticed that the flashing "Press START" stuttered pretty bad, I eventually tracked it to the (last minute) sequence with the jam banner which happens after pressing START to allow the oscillator to run. The function call for my custom animation frame request was duplicated. This is what is causing the problem.
It turns out being able to update the submission was still possible, so I went ahead and patched the fix. I have not seen it happen since, so we should be good, now. I am also crediting you for the fix. THANKS A FREAKIN TON. This slipped completely under the radar and I was depressed a bit at thinking I would be stuck with this browser-killing bug for the next 6 days...
Adding you for credit for finding this!