@HISEnberg Okay I see my error now. I was loading the audio files from the Audio Files folder (using the File System API) and not the Pool which explains why it works in HISE but not in the compiled plugin.
So for anyone else who comes here the answer looks something like this:
const var audioFileList = Engine.loadAudioFilesIntoPool(); // get the audio files from the pool const var AudioReference = Synth.getAudioSampleProcessor("AudioReference"); const var cmb_MatchLoader = Content.getComponent("cmb_MatchLoader"); cmb_MatchLoader.set("items", ""); for (file in audioFileList) { var displayName = file.replace("{PROJECT_FOLDER}", "").replace(".wav", ""); cmb_MatchLoader.addItem(displayName); } inline function oncmb_MatchLoaderControl(component, value) { if (value > 0) { AudioReference.setFile(audioFileList[value - 1]); } } cmb_MatchLoader.setControlCallback(oncmb_MatchLoaderControl);