Thanks for the update to mario bros. Haven't had the issue with bonus mode and full truck since.
I do have another issue that I wanted to wait to see if it would go away with this fix. There appears to be an issue with detecting key release (keyup event). Normally happens at higher level (game speeds), but the characters sometimes will get stuck (normally at the top of the ladder), and not move. Can't find a common "cause" event. Appears that somehow, the sim thinks one of the buttons is pressed even when the keyboard has no keys pressed. Saw the up toggled on one of them when a game ended because of this. The button stayed toggled up, even over a new game start. All down movements were ignored till up was pressed, and the button returned to normal operations.
Again, thanks so much for this childhood trip :)