Thanks for letting me know and helping to improve the quality of this simulation. I've updated the build with a fix for the issues.
You shouldn't now get a second bun appearing in the bottom plate if you quickly press down multiple times on a bun on the bottom (or top) floor. I also fixed the issue of enemies and ladders not moving after the 5th round. And the score will now cycle back to 0 after reaching 19990 points during a game, which I presume would be the case on the actual hardware. The hiscore displayed at the start of subsequent games will however show as 19990 points.