Sorry! Everytime I play it through I like this composition, so to me, that says a lot.
Regarding the shaker, it's the intro few seconds before it finds rhythm. The randomness is in the velocity, the volume of the shaking, and again, this is to me, it feels a bit too dynamic. Is there a reverb on it? I think it muddles it a bit in the beginning, but sits better after that. My random comment was referring to the velocity, not the timing, my bad.
The erhu generally sounds pretty good. The vibrato in the section after the quieter break (short, 4-5 note runs?) is what jumped out. But! Let me say that if you are going for something more playful and toy-like (like many Mario themes are) then it totally works. I guess coming out of the quieter, more delicate section preceding those runs, my mind is expecting something similar. So, since I don't know what exactly you're going for, I can't really say. If your goal is a more natural timbre, I would say ease off the vibrato a hair. But, overall, this a great piece.