Mini lag between sound and image

let me explain,
I film with a sony 720p / 25fps camera (interview) with cable only video sdi. no audio
the sound is taken by a simple xlr microphone connected to a mixer an hdmi audio injector which enters directly into the x2.
the image and sound are very good! But!!!
in the end if we reread the video on facebook we realize that there is a slight difference with the sound! maybe this is my hdmi audio injector that is involved? …
the x2 is configured in 720p 2 mbits / s
best regard

Hmm, that might indeed be the injector. I would recommend bringing in the audio to the camera if you can instead as this is more likely to maintain a perfect sync.