I've read a lot of topics about the app desync audio after rendering, i've noticed this when the video needs a negative time correction (you may notice a second of stop in the video before the appearance of midi notes when you do so). In order to solve this, i export audio and midi, not video, open with VLC, slow down the video and see how much frames the audio is far from where it should be (at 30fps every frame is 0,033 seconds). A bit long as a work, but you can render at minimum quality in order to speed up, correct the audio with the necessary delay or subtraction and then export the correct full video at full quality. Hope this help everybody!