I found a
video of real 3DS VC gameplay that doesn't have the choppy audio, which seems to indicate that's an Encore issue.
It's pretty weird you have to hold a button for at least 2 frames to do anything in this version, and it's compounded by the same input lag Garfield Kart and Ultimate NES Remix have in the core, and maybe other emulated 3DS games I haven't tested. Azahar, another Citra fork, has been tested to
add 2 frames of latency, as in:
Frame 0: Press Left and advance frame (while recording)
Frame 1: L appears at the top of BizHawk's input display and in the Input Log (in DK VC you have to hold Left an additional frame here)
Frames 2-3: Nothing happens, Jumpman still faces right
Frame 4: Jumpman turns Left
Latency wouldn't matter while TASing (other than making the movie 2 frames longer), but it could be a symptom of a larger issue that also affects Donkey Kong's movement. The last post in that latency issue is from an Azahar dev who
confirmed it's a bug with unknown cause.