Hey there,
I've been playing a lot of Galaga lately on the MiSTER and it has some issues with how it calculates the 2nd players score... so keep in mind these cores are not 100% if you come across bugs, be sure to report them
That being said, the DK seems pretty spot on now. It used to have sound issues... and the sounds are a little tinny still, but from a gameplay point, everything is fine.
Like it's said above, barrels can pass through hammers from overhead. It's got to do with how often the game checks collision detection per second. It'll happen on a real board too.
Best bet is to be moving left or right when you try and do that, so if the collision doesn't occur, you move out of the way.
Cheers
Matt