Yes. I can tell you exactly what is wrong.
Your synch is off because the frame rate you 'think' you are recording, isn't the frame rate you are editing at. Consequently when you lay in the audio, it loses synch.
Specs of this camera say that it will record at '30fps' but it is highly likely you are actually shooting at a non-integer frame rate of 29.97fps,...
i think there's surely a short delay/reverberator in this sample that provides that weird slapback / small room space(with more than one repeat).
Also there's some kind of vocoding going on , Im not sure if the vocoder is on the delayed vocal or on the main vocal with the mix turned way low.
Also maybe the vocoder is fed to the short delay.
I think if you ...