Video and audio are not in sync

I have used movie maker in the past to make different and has always worked fine for me but recently when i start playing my edited video from the start before i render it for the first 41.29 seconds the video and the mp3 audio i put in are not sync and when i play the video again but on the second video it was perfectly fine and the rest of my video was fine as well and at first i thought it was just a minor bug that happens before you render the video but even when i rendered it completely the video and audio are still not in sync and I've tried editing and playing my video on a different to see if my other computer was slower but it didn't make a difference 

and the version of MM i have is 2012 16.4.3508.0205 please help me