The hi-score bug only occurs on the final entry....the final byte is not being saved. An update will be done soon. As for issues with Ultimate 1541, I have no way of testing this. If it works on a real 1541 and VICE it suggests a bug with the ultimate.
It's not only the 1541-U, that has a problem here. Played the game on my SD2IEC and "saving the score itself" works and score first can also correctly be seen in score-list and is also saved. But after restarting the game, the score is rounded-down all the time. Very strange. At once, not my real score is shown in the score-list, but a rounded down score to a full hundred. For example, i have 650 points, but only 600 is saved and stand in the scorelist, when game is restarted. Seems like, only the first number (which is a 6 in my example) is saved, but not the digits after the 6. This happens also in emu's, not only on SD2IEC. I guess here are 2 bugs, the rounding thing and a problem on 1541U with saving itself.