Audiokit based apps can't handle some popular soundfonts

Question

I am trying to build a piano app with AK sdk. I have noticed my app, and as well as other AK based apps have trouble handle some popular sf2 files, such as the grand piano in the following preset which works fine in non AK based synthesizer apps: http://schristiancollins.com/soundfonts/GeneralUser_GS_1.44-SoftSynth.zip

What could be the reason?

The code:

sampler = AKAppleSampler()

do {
  try sampler.loadSoundFont("GeneralUser GS FluidSynth", preset: 0 , bank: 0)
  sampler.amplitude = 20

  AudioKit.output = sampler
  try AudioKit.start()

} catch {

}