music out of sync in movie maker

I am trying to make a music video in Windows Movie Maker 2012. however, I have encountered a very important problem. I will try to describe it as best I can. the best way to say it is this- when I move around the video in the build pane using the black vertical bar, the music gets out of sync with the video. for example, If I let the video play for 10 seconds and then grab the bar and rewind 5 seconds, it will arbitrarily move the audio back over 5 seconds. this means that the music also gets out of sync from the wave display, making it impossible to know where I am at. the only way to get back to sync is to start the video from the top again. this results in the video lagging behind the audio, because when editing I sync them perfectly, but once I crank it back to the beginning and play it the audio runs out ahead. can anyone help me here. I would really appreciate it